Systems and methods for efficient Xpath processing

ABSTRACT

The present invention is directed towards systems and methods for efficient Xpath matching of a document comprising Extensible Markup Language (XML) or JavaScript Object Notation (JSON). A Xpath engine identifies an Xpath expression for processing values in the document, which is represented by a stack of nodes. The device may traverse the stack from top to bottom to match each step of the Xpath expression to a type and name of one or more nodes in the stack. The device may store a flag in each node that matches a step of the Xpath expression. Responsive to encountering a leaf node, the device may trace bottom to top from the leaf node to one or more flagged nodes in the stack and compare each flagged node against a corresponding step of the path expression. Responsive to the tracing of the flagged nodes, the device determines if the path expression is matched.

FIELD OF THE DISCLOSURE

The present application generally relates to processing of ExtensibleMarkup Language (XML) Path Language (Xpath) expressions. In particular,the present application relates to systems and methods for efficientXpath matching of an XML or XML-like document.

BACKGROUND

Xpath is a language defined for addressing or accessing elements of anXML document. An XML document may be mapped into or represented by ahierarchy of elements. Accordingly, Xpath operates on this logicalstructure and models an XML document as a tree of nodes. The varioustypes of XML nodes can include element nodes, attribute nodes and textnodes. An Xpath expression is the primary syntactic construct of thelanguage. An Xpath expression can be evaluated to yield an object, suchas a node-set, a Boolean value, a numerical value, or a string. As XMLand XML-like content proliferates and is transmitted across networks, anincreasing amount of such processing is needed. In particular, contentprocessing and receiving devices may extract or process various types ofinformation from XML as well as JSON documents.

BRIEF SUMMARY

The present application is directed towards methods and systems forefficient Xpath processing. In some embodiments, XML or XML-like contentis processed at intermediate or end devices, for example to identify andextract particular elements in XML documents. An XML document may berepresented as a hierarchical stack of nodes or elements. Although Xpathprovides the language capability to define expressions for identifyingXML elements, Xpath processing further requires matching theseexpressions to actual elements in XML documents. Accordingly, in certainembodiments, Xpath expressions can apply to XML, JSON and othersimilarly-structured documents.

In one aspect, the present invention is related to a method forefficient Xpath matching of a document comprising Extensible MarkupLanguage (XML) or JavaScript Object Notation (JSON). The method includesidentifying, by a device, an Xpath expression for processing values inan Extensible Markup Language (XML) or JavaScript Object Notation (JSON)document. The document may be represented by a stack of nodes. Thedevice may traverse the stack of nodes from top to bottom to match eachstep of a path expression of the Xpath expression to a type and name ofone or more nodes in the stack of nodes. The device may store a flagwith each node in the stack of nodes that matches a step of the pathexpression. Responsive to encountering a leaf node, the device may tracebottom to top from the leaf node to one or more flagged nodes in thestack of nodes, and compare each of the one or more flagged nodesagainst a corresponding step of the path expression. The device maydetermine whether the path expression is matched responsive to thetracing of the flagged nodes.

In some embodiments, the device identifies an Xpath expression foridentifying an element or location in the document. The device may matchan expression of each step, including any predicate, with a type and aname of one or more nodes in the stack of nodes. The device may assign astep identifier to each step of the path expression. The device maydetermine that the path expression is not matched if any single step ofthe path expression fails to match any nodes. In some embodiments, thedevice may store a Boolean flag in each node with the stack of nodesthat matches a step of the path expression.

In certain embodiments, the device may perform a loop trace for one ormore descendant axes in the path expression, wherein the loop tracecomprises tracing one or more flagged nodes matching the descendantaxes. The device may determine that there are enough nodes in the stackto match the minimum number of steps remaining in the path expression.Further, the device may determine that the path expression is notmatched if the stack of nodes runs out of nodes before reaching thefirst step of the path expression while tracing bottom to top. Thedevice may determine that the path expression is matched if a node ofthe stack of nodes corresponding to the first step of the pathexpression is flagged.

In one aspect, the present invention is related to a system forefficient Xpath matching of a document comprising Extensible MarkupLanguage (XML) or JavaScript Object Notation (JSON). The system mayinclude a parser for processing a document comprising Extensible MarkupLanguage (XML) or JavaScript Object Notation (JSON). The parser mayrepresent the document as a stack of nodes. The system may include anXpath engine executing on a device. The Xpath engine may include anexpression evaluator identifying an Xpath expression for processingvalues in the document. The Xpath engine may include a node tracer fortraversing the stack of nodes from top to bottom to match each step of apath expression of the Xpath expression to a type and name of one ormore nodes in the stack of nodes. In addition, the node tracer may storea flag with each node in the stack of nodes that matches a step of thepath expression. Responsive to encountering a leaf node, the node tracermay trace bottom to top from the leaf node to one or more flagged nodesin the stack of nodes, comparing each of the one or more flagged nodesagainst a corresponding step of the path expression. The expressionevaluator may determine if the path expression is matched responsive tothe tracing of the flagged nodes.

In some embodiments, the Xpath expression comprises an expression foridentifying an element or location in the document. In certainembodiments, the flag stored with each node in the stack of nodes thatmatches a step of the path expression comprises a Boolean flag. In someembodiments, the expression evaluator matches an expression of eachstep, including any predicate, with a type and a name of one or morenodes in the stack of nodes. The expression evaluator may assign a stepidentifier to each step of the path expression. In certain embodiments,the expression evaluator may determine that the path expression is notmatched if any single step of the path expression fails to match anynodes.

In some embodiments, the node tracer may perform a loop trace for one ormore descendant axes in the path expression, the loop trace comprisingtracing one or more flagged nodes matching the descendant axes. The nodetracer may determine that there are enough nodes in the stack to matchthe minimum number of steps remaining in the path expression. Theexpression evaluator may determine that the path expression is notmatched if the stack of nodes runs out of nodes before reaching thefirst step of the path expression while tracing bottom to top. In someembodiments, the expression evaluator may determine that the pathexpression is matched if a node of the stack of nodes corresponding tothe first step of the path expression is flagged.

The details of various embodiments of the invention are set forth in theaccompanying drawings and the description below.

BRIEF DESCRIPTION OF THE FIGURES

The foregoing and other objects, aspects, features, and advantages ofthe invention will become more apparent and better understood byreferring to the following description taken in conjunction with theaccompanying drawings, in which:

The foregoing and other objects, aspects, features, and advantages ofthe invention will become more apparent and better understood byreferring to the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1A is a block diagram of an embodiment of a network environment fora client to access a server via an appliance;

FIG. 1B is a block diagram of an embodiment of an environment fordelivering a computing environment from a server to a client via anappliance;

FIG. 1C is a block diagram of another embodiment of an environment fordelivering a computing environment from a server to a client via anappliance;

FIG. 1D is a block diagram of another embodiment of an environment fordelivering a computing environment from a server to a client via anappliance;

FIGS. 1E-1H are block diagrams of embodiments of a computing device;

FIG. 2A is a block diagram of an embodiment of an appliance forprocessing communications between a client and a server;

FIG. 2B is a block diagram of another embodiment of an appliance foroptimizing, accelerating, load-balancing and routing communicationsbetween a client and a server;

FIG. 3 is a block diagram of an embodiment of a client for communicatingwith a server via the appliance;

FIG. 4A is a block diagram of an embodiment of a virtualizationenvironment;

FIG. 4B is a block diagram of another embodiment of a virtualizationenvironment;

FIG. 4C is a block diagram of an embodiment of a virtualized appliance;

FIG. 5A are block diagrams of embodiments of approaches to implementingparallelism in a multi-core network appliance;

FIG. 5B is a block diagram of an embodiment of a system utilizing amulti-core network application;

FIG. 5C is a block diagram of an embodiment of an aspect of a multi-corenetwork appliance;

FIG. 6A is a block diagram of an embodiment of a system for efficientXpath processing; and

FIG. 6B is a flow diagram of an embodiment of steps of a method forefficient Xpath processing.

The features and advantages of the present invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements.

DETAILED DESCRIPTION

For purposes of reading the description of the various embodimentsbelow, the following descriptions of the sections of the specificationand their respective contents may be helpful:

-   -   Section A describes a network environment and computing        environment which may be useful for practicing embodiments        described herein;    -   Section B describes embodiments of systems and methods for        delivering a computing environment to a remote user;    -   Section C describes embodiments of systems and methods for        accelerating communications between a client and a server;    -   Section D describes embodiments of systems and methods for        virtualizing an application delivery controller;    -   Section E describes embodiments of systems and methods for        providing a multi-core architecture and environment; and    -   Section F describes embodiments of systems and methods for        efficient Xpath processing.        A. Network and Computing Environment

Prior to discussing the specifics of embodiments of the systems andmethods of an appliance and/or client, it may be helpful to discuss thenetwork and computing environments in which such embodiments may bedeployed. Referring now to FIG. 1A, an embodiment of a networkenvironment is depicted. In brief overview, the network environmentcomprises one or more clients 102 a-102 n (also generally referred to aslocal machine(s) 102, or client(s) 102) in communication with one ormore servers 106 a-106 n (also generally referred to as server(s) 106,or remote machine(s) 106) via one or more networks 104, 104′ (generallyreferred to as network 104). In some embodiments, a client 102communicates with a server 106 via an appliance 200.

Although FIG. 1A shows a network 104 and a network 104′ between theclients 102 and the servers 106, the clients 102 and the servers 106 maybe on the same network 104. The networks 104 and 104′ can be the sametype of network or different types of networks. The network 104 and/orthe network 104′ can be a local-area network (LAN), such as a companyIntranet, a metropolitan area network (MAN), or a wide area network(WAN), such as the Internet or the World Wide Web. In one embodiment,network 104′ may be a private network and network 104 may be a publicnetwork. In some embodiments, network 104 may be a private network andnetwork 104′ a public network. In another embodiment, networks 104 and104′ may both be private networks. In some embodiments, clients 102 maybe located at a branch office of a corporate enterprise communicatingvia a WAN connection over the network 104 to the servers 106 located ata corporate data center.

The network 104 and/or 104′ be any type and/or form of network and mayinclude any of the following: a point to point network, a broadcastnetwork, a wide area network, a local area network, a telecommunicationsnetwork, a data communication network, a computer network, an ATM(Asynchronous Transfer Mode) network, a SONET (Synchronous OpticalNetwork) network, a SDH (Synchronous Digital Hierarchy) network, awireless network and a wireline network. In some embodiments, thenetwork 104 may comprise a wireless link, such as an infrared channel orsatellite band. The topology of the network 104 and/or 104′ may be abus, star, or ring network topology. The network 104 and/or 104′ andnetwork topology may be of any such network or network topology as knownto those ordinarily skilled in the art capable of supporting theoperations described herein.

As shown in FIG. 1A, the appliance 200, which also may be referred to asan interface unit 200 or gateway 200, is shown between the networks 104and 104′. In some embodiments, the appliance 200 may be located onnetwork 104. For example, a branch office of a corporate enterprise maydeploy an appliance 200 at the branch office. In other embodiments, theappliance 200 may be located on network 104′. For example, an appliance200 may be located at a corporate data center. In yet anotherembodiment, a plurality of appliances 200 may be deployed on network104. In some embodiments, a plurality of appliances 200 may be deployedon network 104′. In one embodiment, a first appliance 200 communicateswith a second appliance 200′. In other embodiments, the appliance 200could be a part of any client 102 or server 106 on the same or differentnetwork 104,104′ as the client 102. One or more appliances 200 may belocated at any point in the network or network communications pathbetween a client 102 and a server 106.

In some embodiments, the appliance 200 comprises any of the networkdevices manufactured by Citrix Systems, Inc. of Ft. Lauderdale Fla.,referred to as Citrix NetScaler devices. In other embodiments, theappliance 200 includes any of the product embodiments referred to asWebAccelerator and BigIP manufactured by F5 Networks, Inc. of Seattle,Wash. In another embodiment, the appliance 205 includes any of the DXacceleration device platforms and/or the SSL VPN series of devices, suchas SA 700, SA 2000, SA 4000, and SA 6000 devices manufactured by JuniperNetworks, Inc. of Sunnyvale, Calif. In yet another embodiment, theappliance 200 includes any application acceleration and/or securityrelated appliances and/or software manufactured by Cisco Systems, Inc.of San Jose, Calif., such as the Cisco ACE Application Control EngineModule service software and network modules, and Cisco AVS SeriesApplication Velocity System.

In one embodiment, the system may include multiple, logically-groupedservers 106. In these embodiments, the logical group of servers may bereferred to as a server farm 38. In some of these embodiments, theserves 106 may be geographically dispersed. In some cases, a farm 38 maybe administered as a single entity. In other embodiments, the serverfarm 38 comprises a plurality of server farms 38. In one embodiment, theserver farm executes one or more applications on behalf of one or moreclients 102.

The servers 106 within each farm 38 can be heterogeneous. One or more ofthe servers 106 can operate according to one type of operating systemplatform (e.g., WINDOWS NT, manufactured by Microsoft Corp. of Redmond,Wash.), while one or more of the other servers 106 can operate onaccording to another type of operating system platform (e.g., Unix orLinux). The servers 106 of each farm 38 do not need to be physicallyproximate to another server 106 in the same farm 38. Thus, the group ofservers 106 logically grouped as a farm 38 may be interconnected using awide-area network (WAN) connection or medium-area network (MAN)connection. For example, a farm 38 may include servers 106 physicallylocated in different continents or different regions of a continent,country, state, city, campus, or room. Data transmission speeds betweenservers 106 in the farm 38 can be increased if the servers 106 areconnected using a local-area network (LAN) connection or some form ofdirect connection.

Servers 106 may be referred to as a file server, application server, webserver, proxy server, or gateway server. In some embodiments, a server106 may have the capacity to function as either an application server oras a master application server. In one embodiment, a server 106 mayinclude an Active Directory. The clients 102 may also be referred to asclient nodes or endpoints. In some embodiments, a client 102 has thecapacity to function as both a client node seeking access toapplications on a server and as an application server providing accessto hosted applications for other clients 102 a-102 n.

In some embodiments, a client 102 communicates with a server 106. In oneembodiment, the client 102 communicates directly with one of the servers106 in a farm 38. In another embodiment, the client 102 executes aprogram neighborhood application to communicate with a server 106 in afarm 38. In still another embodiment, the server 106 provides thefunctionality of a master node. In some embodiments, the client 102communicates with the server 106 in the farm 38 through a network 104.Over the network 104, the client 102 can, for example, request executionof various applications hosted by the servers 106 a-106 n in the farm 38and receive output of the results of the application execution fordisplay. In some embodiments, only the master node provides thefunctionality required to identify and provide address informationassociated with a server 106′ hosting a requested application.

In one embodiment, the server 106 provides functionality of a webserver. In another embodiment, the server 106 a receives requests fromthe client 102, forwards the requests to a second server 106 b andresponds to the request by the client 102 with a response to the requestfrom the server 106 b. In still another embodiment, the server 106acquires an enumeration of applications available to the client 102 andaddress information associated with a server 106 hosting an applicationidentified by the enumeration of applications. In yet anotherembodiment, the server 106 presents the response to the request to theclient 102 using a web interface. In one embodiment, the client 102communicates directly with the server 106 to access the identifiedapplication. In another embodiment, the client 102 receives applicationoutput data, such as display data, generated by an execution of theidentified application on the server 106.

Referring now to FIG. 1B, an embodiment of a network environmentdeploying multiple appliances 200 is depicted. A first appliance 200 maybe deployed on a first network 104 and a second appliance 200′ on asecond network 104′. For example a corporate enterprise may deploy afirst appliance 200 at a branch office and a second appliance 200′ at adata center. In another embodiment, the first appliance 200 and secondappliance 200′ are deployed on the same network 104 or network 104. Forexample, a first appliance 200 may be deployed for a first server farm38, and a second appliance 200 may be deployed for a second server farm38′. In another example, a first appliance 200 may be deployed at afirst branch office while the second appliance 200′ is deployed at asecond branch office'. In some embodiments, the first appliance 200 andsecond appliance 200′ work in cooperation or in conjunction with eachother to accelerate network traffic or the delivery of application anddata between a client and a server

Referring now to FIG. 1C, another embodiment of a network environmentdeploying the appliance 200 with one or more other types of appliances,such as between one or more WAN optimization appliance 205, 205′ isdepicted. For example a first WAN optimization appliance 205 is shownbetween networks 104 and 104′ and a second WAN optimization appliance205′ may be deployed between the appliance 200 and one or more servers106. By way of example, a corporate enterprise may deploy a first WANoptimization appliance 205 at a branch office and a second WANoptimization appliance 205′ at a data center. In some embodiments, theappliance 205 may be located on network 104′. In other embodiments, theappliance 205′ may be located on network 104. In some embodiments, theappliance 205′ may be located on network 104′ or network 104″. In oneembodiment, the appliance 205 and 205′ are on the same network. Inanother embodiment, the appliance 205 and 205′ are on differentnetworks. In another example, a first WAN optimization appliance 205 maybe deployed for a first server farm 38 and a second WAN optimizationappliance 205′ for a second server farm 38′

In one embodiment, the appliance 205 is a device for accelerating,optimizing or otherwise improving the performance, operation, or qualityof service of any type and form of network traffic, such as traffic toand/or from a WAN connection. In some embodiments, the appliance 205 isa performance enhancing proxy. In other embodiments, the appliance 205is any type and form of WAN optimization or acceleration device,sometimes also referred to as a WAN optimization controller. In oneembodiment, the appliance 205 is any of the product embodiments referredto as WANScaler manufactured by Citrix Systems, Inc. of Ft. Lauderdale,Fla. In other embodiments, the appliance 205 includes any of the productembodiments referred to as BIG-IP link controller and WANjetmanufactured by F5 Networks, Inc. of Seattle, Wash. In anotherembodiment, the appliance 205 includes any of the WX and WXC WANacceleration device platforms manufactured by Juniper Networks, Inc. ofSunnyvale, Calif. In some embodiments, the appliance 205 includes any ofthe steelhead line of WAN optimization appliances manufactured byRiverbed Technology of San Francisco, Calif. In other embodiments, theappliance 205 includes any of the WAN related devices manufactured byExpand Networks Inc. of Roseland, N.J. In one embodiment, the appliance205 includes any of the WAN related appliances manufactured by PacketeerInc. of Cupertino, Calif., such as the PacketShaper, iShared, and SkyXproduct embodiments provided by Packeteer. In yet another embodiment,the appliance 205 includes any WAN related appliances and/or softwaremanufactured by Cisco Systems, Inc. of San Jose, Calif., such as theCisco Wide Area Network Application Services software and networkmodules, and Wide Area Network engine appliances.

In one embodiment, the appliance 205 provides application and dataacceleration services for branch-office or remote offices. In oneembodiment, the appliance 205 includes optimization of Wide Area FileServices (WAFS). In another embodiment, the appliance 205 acceleratesthe delivery of files, such as via the Common Internet File System(CIFS) protocol. In other embodiments, the appliance 205 providescaching in memory and/or storage to accelerate delivery of applicationsand data. In one embodiment, the appliance 205 provides compression ofnetwork traffic at any level of the network stack or at any protocol ornetwork layer. In another embodiment, the appliance 205 providestransport layer protocol optimizations, flow control, performanceenhancements or modifications and/or management to accelerate deliveryof applications and data over a WAN connection. For example, in oneembodiment, the appliance 205 provides Transport Control Protocol (TCP)optimizations. In other embodiments, the appliance 205 providesoptimizations, flow control, performance enhancements or modificationsand/or management for any session or application layer protocol.

In another embodiment, the appliance 205 encoded any type and form ofdata or information into custom or standard TCP and/or IP header fieldsor option fields of network packet to announce presence, functionalityor capability to another appliance 205′. In another embodiment, anappliance 205′ may communicate with another appliance 205′ using dataencoded in both TCP and/or IP header fields or options. For example, theappliance may use TCP option(s) or IP header fields or options tocommunicate one or more parameters to be used by the appliances 205,205′ in performing functionality, such as WAN acceleration, or forworking in conjunction with each other.

In some embodiments, the appliance 200 preserves any of the informationencoded in TCP and/or IP header and/or option fields communicatedbetween appliances 205 and 205′. For example, the appliance 200 mayterminate a transport layer connection traversing the appliance 200,such as a transport layer connection from between a client and a servertraversing appliances 205 and 205′. In one embodiment, the appliance 200identifies and preserves any encoded information in a transport layerpacket transmitted by a first appliance 205 via a first transport layerconnection and communicates a transport layer packet with the encodedinformation to a second appliance 205′ via a second transport layerconnection.

Referring now to FIG. 1D, a network environment for delivering and/oroperating a computing environment on a client 102 is depicted. In someembodiments, a server 106 includes an application delivery system 190for delivering a computing environment or an application and/or datafile to one or more clients 102. In brief overview, a client 102 is incommunication with a server 106 via network 104, 104′ and appliance 200.For example, the client 102 may reside in a remote office of a company,e.g., a branch office, and the server 106 may reside at a corporate datacenter. The client 102 comprises a client agent 120, and a computingenvironment 15. The computing environment 15 may execute or operate anapplication that accesses, processes or uses a data file. The computingenvironment 15, application and/or data file may be delivered via theappliance 200 and/or the server 106.

In some embodiments, the appliance 200 accelerates delivery of acomputing environment 15, or any portion thereof, to a client 102. Inone embodiment, the appliance 200 accelerates the delivery of thecomputing environment 15 by the application delivery system 190. Forexample, the embodiments described herein may be used to acceleratedelivery of a streaming application and data file processable by theapplication from a central corporate data center to a remote userlocation, such as a branch office of the company. In another embodiment,the appliance 200 accelerates transport layer traffic between a client102 and a server 106. The appliance 200 may provide accelerationtechniques for accelerating any transport layer payload from a server106 to a client 102, such as: 1) transport layer connection pooling, 2)transport layer connection multiplexing, 3) transport control protocolbuffering, 4) compression and 5) caching. In some embodiments, theappliance 200 provides load balancing of servers 106 in responding torequests from clients 102. In other embodiments, the appliance 200 actsas a proxy or access server to provide access to the one or more servers106. In another embodiment, the appliance 200 provides a secure virtualprivate network connection from a first network 104 of the client 102 tothe second network 104′ of the server 106, such as an SSL VPNconnection. It yet other embodiments, the appliance 200 providesapplication firewall security, control and management of the connectionand communications between a client 102 and a server 106.

In some embodiments, the application delivery management system 190provides application delivery techniques to deliver a computingenvironment to a desktop of a user, remote or otherwise, based on aplurality of execution methods and based on any authentication andauthorization policies applied via a policy engine 195. With thesetechniques, a remote user may obtain a computing environment and accessto server stored applications and data files from any network connecteddevice 100. In one embodiment, the application delivery system 190 mayreside or execute on a server 106. In another embodiment, theapplication delivery system 190 may reside or execute on a plurality ofservers 106 a-106 n. In some embodiments, the application deliverysystem 190 may execute in a server farm 38. In one embodiment, theserver 106 executing the application delivery system 190 may also storeor provide the application and data file. In another embodiment, a firstset of one or more servers 106 may execute the application deliverysystem 190, and a different server 106 n may store or provide theapplication and data file. In some embodiments, each of the applicationdelivery system 190, the application, and data file may reside or belocated on different servers. In yet another embodiment, any portion ofthe application delivery system 190 may reside, execute or be stored onor distributed to the appliance 200, or a plurality of appliances.

The client 102 may include a computing environment 15 for executing anapplication that uses or processes a data file. The client 102 vianetworks 104, 104′ and appliance 200 may request an application and datafile from the server 106. In one embodiment, the appliance 200 mayforward a request from the client 102 to the server 106. For example,the client 102 may not have the application and data file stored oraccessible locally. In response to the request, the application deliverysystem 190 and/or server 106 may deliver the application and data fileto the client 102. For example, in one embodiment, the server 106 maytransmit the application as an application stream to operate incomputing environment 15 on client 102.

In some embodiments, the application delivery system 190 comprises anyportion of the Citrix Access Suite™ by Citrix Systems, Inc., such as theMetaFrame or Citrix Presentation Server™ and/or any of the Microsoft®Windows Terminal Services manufactured by the Microsoft Corporation. Inone embodiment, the application delivery system 190 may deliver one ormore applications to clients 102 or users via a remote-display protocolor otherwise via remote-based or server-based computing. In anotherembodiment, the application delivery system 190 may deliver one or moreapplications to clients or users via steaming of the application.

In one embodiment, the application delivery system 190 includes a policyengine 195 for controlling and managing the access to, selection ofapplication execution methods and the delivery of applications. In someembodiments, the policy engine 195 determines the one or moreapplications a user or client 102 may access. In another embodiment, thepolicy engine 195 determines how the application should be delivered tothe user or client 102, e.g., the method of execution. In someembodiments, the application delivery system 190 provides a plurality ofdelivery techniques from which to select a method of applicationexecution, such as a server-based computing, streaming or delivering theapplication locally to the client 120 for local execution.

In one embodiment, a client 102 requests execution of an applicationprogram and the application delivery system 190 comprising a server 106selects a method of executing the application program. In someembodiments, the server 106 receives credentials from the client 102. Inanother embodiment, the server 106 receives a request for an enumerationof available applications from the client 102. In one embodiment, inresponse to the request or receipt of credentials, the applicationdelivery system 190 enumerates a plurality of application programsavailable to the client 102. The application delivery system 190receives a request to execute an enumerated application. The applicationdelivery system 190 selects one of a predetermined number of methods forexecuting the enumerated application, for example, responsive to apolicy of a policy engine. The application delivery system 190 mayselect a method of execution of the application enabling the client 102to receive application-output data generated by execution of theapplication program on a server 106. The application delivery system 190may select a method of execution of the application enabling the localmachine 10 to execute the application program locally after retrieving aplurality of application files comprising the application. In yetanother embodiment, the application delivery system 190 may select amethod of execution of the application to stream the application via thenetwork 104 to the client 102.

A client 102 may execute, operate or otherwise provide an application,which can be any type and/or form of software, program, or executableinstructions such as any type and/or form of web browser, web-basedclient, client-server application, a thin-client computing client, anActiveX control, or a Java applet, or any other type and/or form ofexecutable instructions capable of executing on client 102. In someembodiments, the application may be a server-based or a remote-basedapplication executed on behalf of the client 102 on a server 106. In oneembodiments the server 106 may display output to the client 102 usingany thin-client or remote-display protocol, such as the IndependentComputing Architecture (ICA) protocol manufactured by Citrix Systems,Inc. of Ft. Lauderdale, Fla. or the Remote Desktop Protocol (RDP)manufactured by the Microsoft Corporation of Redmond, Wash. Theapplication can use any type of protocol and it can be, for example, anHTTP client, an FTP client, an Oscar client, or a Telnet client. Inother embodiments, the application comprises any type of softwarerelated to VoIP communications, such as a soft IP telephone. In furtherembodiments, the application comprises any application related toreal-time data communications, such as applications for streaming videoand/or audio.

In some embodiments, the server 106 or a server farm 38 may be runningone or more applications, such as an application providing a thin-clientcomputing or remote display presentation application. In one embodiment,the server 106 or server farm 38 executes as an application, any portionof the Citrix Access Suite™ by Citrix Systems, Inc., such as theMetaFrame or Citrix Presentation Server™, and/or any of the Microsoft®Windows Terminal Services manufactured by the Microsoft Corporation. Inone embodiment, the application is an ICA client, developed by CitrixSystems, Inc. of Fort Lauderdale, Fla. In other embodiments, theapplication includes a Remote Desktop (RDP) client, developed byMicrosoft Corporation of Redmond, Wash. Also, the server 106 may run anapplication, which for example, may be an application server providingemail services such as Microsoft Exchange manufactured by the MicrosoftCorporation of Redmond, Wash., a web or Internet server, or a desktopsharing server, or a collaboration server. In some embodiments, any ofthe applications may comprise any type of hosted service or products,such as GoToMeeting™ provided by Citrix Online Division, Inc. of SantaBarbara, Calif., WebEx™ provided by WebEx, Inc. of Santa Clara, Calif.,or Microsoft Office Live Meeting provided by Microsoft Corporation ofRedmond, Wash.

Still referring to FIG. 1D, an embodiment of the network environment mayinclude a monitoring server 106A. The monitoring server 106A may includeany type and form performance monitoring service 198. The performancemonitoring service 198 may include monitoring, measurement and/ormanagement software and/or hardware, including data collection,aggregation, analysis, management and reporting. In one embodiment, theperformance monitoring service 198 includes one or more monitoringagents 197. The monitoring agent 197 includes any software, hardware orcombination thereof for performing monitoring, measurement and datacollection activities on a device, such as a client 102, server 106 oran appliance 200, 205. In some embodiments, the monitoring agent 197includes any type and form of script, such as Visual Basic script, orJavascript. In one embodiment, the monitoring agent 197 executestransparently to any application and/or user of the device. In someembodiments, the monitoring agent 197 is installed and operatedunobtrusively to the application or client. In yet another embodiment,the monitoring agent 197 is installed and operated without anyinstrumentation for the application or device.

In some embodiments, the monitoring agent 197 monitors, measures andcollects data on a predetermined frequency. In other embodiments, themonitoring agent 197 monitors, measures and collects data based upondetection of any type and form of event. For example, the monitoringagent 197 may collect data upon detection of a request for a web page orreceipt of an HTTP response. In another example, the monitoring agent197 may collect data upon detection of any user input events, such as amouse click. The monitoring agent 197 may report or provide anymonitored, measured or collected data to the monitoring service 198. Inone embodiment, the monitoring agent 197 transmits information to themonitoring service 198 according to a schedule or a predeterminedfrequency. In another embodiment, the monitoring agent 197 transmitsinformation to the monitoring service 198 upon detection of an event.

In some embodiments, the monitoring service 198 and/or monitoring agent197 performs monitoring and performance measurement of any networkresource or network infrastructure element, such as a client, server,server farm, appliance 200, appliance 205, or network connection. In oneembodiment, the monitoring service 198 and/or monitoring agent 197performs monitoring and performance measurement of any transport layerconnection, such as a TCP or UDP connection. In another embodiment, themonitoring service 198 and/or monitoring agent 197 monitors and measuresnetwork latency. In yet one embodiment, the monitoring service 198and/or monitoring agent 197 monitors and measures bandwidth utilization.

In other embodiments, the monitoring service 198 and/or monitoring agent197 monitors and measures end-user response times. In some embodiments,the monitoring service 198 performs monitoring and performancemeasurement of an application. In another embodiment, the monitoringservice 198 and/or monitoring agent 197 performs monitoring andperformance measurement of any session or connection to the application.In one embodiment, the monitoring service 198 and/or monitoring agent197 monitors and measures performance of a browser. In anotherembodiment, the monitoring service 198 and/or monitoring agent 197monitors and measures performance of HTTP based transactions. In someembodiments, the monitoring service 198 and/or monitoring agent 197monitors and measures performance of a Voice over IP (VoIP) applicationor session. In other embodiments, the monitoring service 198 and/ormonitoring agent 197 monitors and measures performance of a remotedisplay protocol application, such as an ICA client or RDP client. Inyet another embodiment, the monitoring service 198 and/or monitoringagent 197 monitors and measures performance of any type and form ofstreaming media. In still a further embodiment, the monitoring service198 and/or monitoring agent 197 monitors and measures performance of ahosted application or a Software-As-A-Service (SaaS) delivery model.

In some embodiments, the monitoring service 198 and/or monitoring agent197 performs monitoring and performance measurement of one or moretransactions, requests or responses related to application. In otherembodiments, the monitoring service 198 and/or monitoring agent 197monitors and measures any portion of an application layer stack, such asany .NET or J2EE calls. In one embodiment, the monitoring service 198and/or monitoring agent 197 monitors and measures database or SQLtransactions. In yet another embodiment, the monitoring service 198and/or monitoring agent 197 monitors and measures any method, functionor application programming interface (API) call.

In one embodiment, the monitoring service 198 and/or monitoring agent197 performs monitoring and performance measurement of a delivery ofapplication and/or data from a server to a client via one or moreappliances, such as appliance 200 and/or appliance 205. In someembodiments, the monitoring service 198 and/or monitoring agent 197monitors and measures performance of delivery of a virtualizedapplication. In other embodiments, the monitoring service 198 and/ormonitoring agent 197 monitors and measures performance of delivery of astreaming application. In another embodiment, the monitoring service 198and/or monitoring agent 197 monitors and measures performance ofdelivery of a desktop application to a client and/or the execution ofthe desktop application on the client. In another embodiment, themonitoring service 198 and/or monitoring agent 197 monitors and measuresperformance of a client/server application.

In one embodiment, the monitoring service 198 and/or monitoring agent197 is designed and constructed to provide application performancemanagement for the application delivery system 190. For example, themonitoring service 198 and/or monitoring agent 197 may monitor, measureand manage the performance of the delivery of applications via theCitrix Presentation Server. In this example, the monitoring service 198and/or monitoring agent 197 monitors individual ICA sessions. Themonitoring service 198 and/or monitoring agent 197 may measure the totaland per session system resource usage, as well as application andnetworking performance. The monitoring service 198 and/or monitoringagent 197 may identify the active servers for a given user and/or usersession. In some embodiments, the monitoring service 198 and/ormonitoring agent 197 monitors back-end connections between theapplication delivery system 190 and an application and/or databaseserver. The monitoring service 198 and/or monitoring agent 197 maymeasure network latency, delay and volume per user-session or ICAsession.

In some embodiments, the monitoring service 198 and/or monitoring agent197 measures and monitors memory usage for the application deliverysystem 190, such as total memory usage, per user session and/or perprocess. In other embodiments, the monitoring service 198 and/ormonitoring agent 197 measures and monitors CPU usage the applicationdelivery system 190, such as total CPU usage, per user session and/orper process. In another embodiments, the monitoring service 198 and/ormonitoring agent 197 measures and monitors the time required to log-into an application, a server, or the application delivery system, such asCitrix Presentation Server. In one embodiment, the monitoring service198 and/or monitoring agent 197 measures and monitors the duration auser is logged into an application, a server, or the applicationdelivery system 190. In some embodiments, the monitoring service 198and/or monitoring agent 197 measures and monitors active and inactivesession counts for an application, server or application delivery systemsession. In yet another embodiment, the monitoring service 198 and/ormonitoring agent 197 measures and monitors user session latency.

In yet further embodiments, the monitoring service 198 and/or monitoringagent 197 measures and monitors measures and monitors any type and formof server metrics. In one embodiment, the monitoring service 198 and/ormonitoring agent 197 measures and monitors metrics related to systemmemory, CPU usage, and disk storage. In another embodiment, themonitoring service 198 and/or monitoring agent 197 measures and monitorsmetrics related to page faults, such as page faults per second. In otherembodiments, the monitoring service 198 and/or monitoring agent 197measures and monitors round-trip time metrics. In yet anotherembodiment, the monitoring service 198 and/or monitoring agent 197measures and monitors metrics related to application crashes, errorsand/or hangs.

In some embodiments, the monitoring service 198 and monitoring agent 198includes any of the product embodiments referred to as EdgeSightmanufactured by Citrix Systems, Inc. of Ft. Lauderdale, Fla. In anotherembodiment, the performance monitoring service 198 and/or monitoringagent 198 includes any portion of the product embodiments referred to asthe TrueView product suite manufactured by the Symphoniq Corporation ofPalo Alto, Calif. In one embodiment, the performance monitoring service198 and/or monitoring agent 198 includes any portion of the productembodiments referred to as the TeaLeaf CX product suite manufactured bythe TeaLeaf Technology Inc. of San Francisco, Calif. In otherembodiments, the performance monitoring service 198 and/or monitoringagent 198 includes any portion of the business service managementproducts, such as the BMC Performance Manager and Patrol products,manufactured by BMC Software, Inc. of Houston, Tex.

The client 102, server 106, and appliance 200 may be deployed as and/orexecuted on any type and form of computing device, such as a computer,network device or appliance capable of communicating on any type andform of network and performing the operations described herein. FIGS. 1Eand 1F depict block diagrams of a computing device 100 useful forpracticing an embodiment of the client 102, server 106 or appliance 200.As shown in FIGS. 1E and 1F, each computing device 100 includes acentral processing unit 101, and a main memory unit 122. As shown inFIG. 1E, a computing device 100 may include a visual display device 124,a keyboard 126 and/or a pointing device 127, such as a mouse. Eachcomputing device 100 may also include additional optional elements, suchas one or more input/output devices 130 a-130 b (generally referred tousing reference numeral 130), and a cache memory 140 in communicationwith the central processing unit 101.

The central processing unit 101 is any logic circuitry that responds toand processes instructions fetched from the main memory unit 122. Inmany embodiments, the central processing unit is provided by amicroprocessor unit, such as: those manufactured by Intel Corporation ofMountain View, Calif.; those manufactured by Motorola Corporation ofSchaumburg, Ill.; those manufactured by Transmeta Corporation of SantaClara, Calif.; the RS/6000 processor, those manufactured byInternational Business Machines of White Plains, N.Y.; or thosemanufactured by Advanced Micro Devices of Sunnyvale, Calif. Thecomputing device 100 may be based on any of these processors, or anyother processor capable of operating as described herein.

Main memory unit 122 may be one or more memory chips capable of storingdata and allowing any storage location to be directly accessed by themicroprocessor 101, such as Static random access memory (SRAM), BurstSRAM or SynchBurst SRAM (BSRAM), Dynamic random access memory (DRAM),Fast Page Mode DRAM (FPM DRAM), Enhanced DRAM (EDRAM), Extended DataOutput RAM (EDO RAM), Extended Data Output DRAM (EDO DRAM), BurstExtended Data Output DRAM (BEDO DRAM); Enhanced DRAM (EDRAM),synchronous DRAM (SDRAM), JEDEC SRAM, PC 100 SDRAM, Double Data RateSDRAM (DDR SDRAM), Enhanced SDRAM (ESDRAM), SyncLink DRAM (SLDRAM),Direct Rambus DRAM (DRDRAM), or Ferroelectric RAM (FRAM). The mainmemory 122 may be based on any of the above described memory chips, orany other available memory chips capable of operating as describedherein. In the embodiment shown in FIG. 1E, the processor 101communicates with main memory 122 via a system bus 150 (described inmore detail below). FIG. 1F depicts an embodiment of a computing device100 in which the processor communicates directly with main memory 122via a memory port 103. For example, in FIG. 1F the main memory 122 maybe DRDRAM.

FIG. 1F depicts an embodiment in which the main processor 101communicates directly with cache memory 140 via a secondary bus,sometimes referred to as a backside bus. In other embodiments, the mainprocessor 101 communicates with cache memory 140 using the system bus150. Cache memory 140 typically has a faster response time than mainmemory 122 and is typically provided by SRAM, BSRAM, or EDRAM. In theembodiment shown in FIG. 1F, the processor 101 communicates with variousI/O devices 130 via a local system bus 150. Various busses may be usedto connect the central processing unit 101 to any of the I/O devices130, including a VESA VL bus, an ISA bus, an EISA bus, a MicroChannelArchitecture (MCA) bus, a PCI bus, a PCI-X bus, a PCI-Express bus, or aNuBus. For embodiments in which the I/O device is a video display 124,the processor 101 may use an Advanced Graphics Port (AGP) to communicatewith the display 124. FIG. 1F depicts an embodiment of a computer 100 inwhich the main processor 101 communicates directly with I/O device 130 bvia HyperTransport, Rapid I/O, or InfiniBand. FIG. 1F also depicts anembodiment in which local busses and direct communication are mixed: theprocessor 101 communicates with I/O device 130 b using a local.interconnect bus while communicating with I/O device 130 a directly.

The computing device 100 may support any suitable installation device116, such as a floppy disk drive for receiving floppy disks such as3.5-inch, 5.25-inch disks or ZIP disks, a CD-ROM drive, a CD-R/RW drive,a DVD-ROM drive, tape drives of various formats, USB device, hard-driveor any other device suitable for installing software and programs suchas any client agent 120, or portion thereof. The computing device 100may further comprise a storage device 128, such as one or more hard diskdrives or redundant arrays of independent disks, for storing anoperating system and other related software, and for storing applicationsoftware programs such as any program related to the client agent 120.Optionally, any of the installation devices 116 could also be used asthe storage device 128. Additionally, the operating system and thesoftware can be run from a bootable medium, for example, a bootable CD,such as KNOPPIX®, a bootable CD for GNU/Linux that is available as aGNU/Linux distribution from knoppix.net.

Furthermore, the computing device 100 may include a network interface118 to interface to a Local Area Network (LAN), Wide Area Network (WAN)or the Internet through a variety of connections including, but notlimited to, standard telephone lines, LAN or WAN links (e.g., 802.11,T1, T3, 56 kb, X.25), broadband connections (e.g., ISDN, Frame Relay,ATM), wireless connections, or some combination of any or all of theabove. The network interface 118 may comprise a built-in networkadapter, network interface card, PCMCIA network card, card bus networkadapter, wireless network adapter, USB network adapter, modem or anyother device suitable for interfacing the computing device 100 to anytype of network capable of communication and performing the operationsdescribed herein.

A wide variety of I/O devices 130 a-130 n may be present in thecomputing device 100. Input devices include keyboards, mice, trackpads,trackballs, microphones, and drawing tablets. Output devices includevideo displays, speakers, inkjet printers, laser printers, anddye-sublimation printers. The I/O devices 130 may be controlled by anI/O controller 123 as shown in FIG. 1E. The I/O controller may controlone or more I/O devices such as a keyboard 126 and a pointing device127, e.g., a mouse or optical pen. Furthermore, an I/O device may alsoprovide storage 128 and/or an installation medium 116 for the computingdevice 100. In still other embodiments, the computing device 100 mayprovide USB connections to receive handheld USB storage devices such asthe USB Flash Drive line of devices manufactured by Twintech Industry,Inc. of Los Alamitos, Calif.

In some embodiments, the computing device 100 may comprise or beconnected to multiple display devices 124 a-124 n, which each may be ofthe same or different type and/or form. As such, any of the I/O devices130 a-130 n and/or the I/O controller 123 may comprise any type and/orform of suitable hardware, software, or combination of hardware andsoftware to support, enable or provide for the connection and use ofmultiple display devices 124 a-124 n by the computing device 100. Forexample, the computing device 100 may include any type and/or form ofvideo adapter, video card, driver, and/or library to interface,communicate, connect or otherwise use the display devices 124 a-124 n.In one embodiment, a video adapter may comprise multiple connectors tointerface to multiple display devices 124 a-124 n. In other embodiments,the computing device 100 may include multiple video adapters, with eachvideo adapter connected to one or more of the display devices 124 a-124n. In some embodiments, any portion of the operating system of thecomputing device 100 may be configured for using multiple displays 124a-124 n. In other embodiments, one or more of the display devices 124a-124 n may be provided by one or more other computing devices, such ascomputing devices 100 a and 100 b connected to the computing device 100,for example, via a network. These embodiments may include any type ofsoftware designed and constructed to use another computer's displaydevice as a second display device 124 a for the computing device 100.One ordinarily skilled in the art will recognize and appreciate thevarious ways and embodiments that a computing device 100 may beconfigured to have multiple display devices 124 a-124 n.

In further embodiments, an I/O device 130 may be a bridge 170 betweenthe system bus 150 and an external communication bus, such as a USB bus,an Apple Desktop Bus, an RS-232 serial connection, a SCSI bus, aFireWire bus, a FireWire 800 bus, an Ethernet bus, an AppleTalk bus, aGigabit Ethernet bus, an Asynchronous Transfer Mode bus, a HIPPI bus, aSuper HIPPI bus, a SerialPlus bus, a SCI/LAMP bus, a FibreChannel bus,or a Serial Attached small computer system interface bus.

A computing device 100 of the sort depicted in FIGS. 1E and 1F typicallyoperate under the control of operating systems, which control schedulingof tasks and access to system resources. The computing device 100 can berunning any operating system such as any of the versions of theMicrosoft® Windows operating systems, the different releases of the Unixand Linux operating systems, any version of the Mac OS® for Macintoshcomputers, any embedded operating system, any real-time operatingsystem, any open source operating system, any proprietary operatingsystem, any operating systems for mobile computing devices, or any otheroperating system capable of running on the computing device andperforming the operations described herein. Typical operating systemsinclude: WINDOWS 3.x, WINDOWS 95, WINDOWS 98, WINDOWS 2000, WINDOWS NT3.51, WINDOWS NT 4.0, WINDOWS CE, and WINDOWS XP, all of which aremanufactured by Microsoft Corporation of Redmond, Wash.; MacOS,manufactured by Apple Computer of Cupertino, California; OS/2,manufactured by International Business Machines of Armonk, N.Y.; andLinux, a freely-available operating system distributed by Caldera Corp.of Salt Lake City, Utah, or any type and/or form of a Unix operatingsystem, among others.

In other embodiments, the computing device 100 may have differentprocessors, operating systems, and input devices consistent with thedevice. For example, in one embodiment the computer 100 is a Treo 180,270, 1060, 600 or 650 smart phone manufactured by Palm, Inc. In thisembodiment, the Treo smart phone is operated under the control of thePalmOS operating system and includes a stylus input device as well as afive-way navigator device. Moreover, the computing device 100 can be anyworkstation, desktop computer, laptop or notebook computer, server,handheld computer, mobile telephone, any other computer, or other formof computing or telecommunications device that is capable ofcommunication and that has sufficient processor power and memorycapacity to perform the operations described herein.

As shown in FIG. 1G, the computing device 100 may comprise multipleprocessors and may provide functionality for simultaneous execution ofinstructions or for simultaneous execution of one instruction on morethan one piece of data. In some embodiments, the computing device 100may comprise a parallel processor with one or more cores. In one ofthese embodiments, the computing device 100 is a shared memory paralleldevice, with multiple processors and/or multiple processor cores,accessing all available memory as a single global address space. Inanother of these embodiments, the computing device 100 is a distributedmemory parallel device with multiple processors each accessing localmemory only. In still another of these embodiments, the computing device100 has both some memory which is shared and some memory which can onlybe accessed by particular processors or subsets of processors. In stilleven another of these embodiments, the computing device 100, such as amulti-core microprocessor, combines two or more independent processorsinto a single package, often a single integrated circuit (IC). In yetanother of these embodiments, the computing device 100 includes a chiphaving a CELL BROADBAND ENGINE architecture and including a Powerprocessor element and a plurality of synergistic processing elements,the Power processor element and the plurality of synergistic processingelements linked together by an internal high speed bus, which may bereferred to as an element interconnect bus.

In some embodiments, the processors provide functionality for executionof a single instruction simultaneously on multiple pieces of data(SIMD). In other embodiments, the processors provide functionality forexecution of multiple instructions simultaneously on multiple pieces ofdata (MIMD). In still other embodiments, the processor may use anycombination of SIMD and MIMD cores in a single device.

In some embodiments, the computing device 100 may comprise a graphicsprocessing unit. In one of these embodiments, depicted in FIG. 1H, thecomputing device 100 includes at least one central processing unit 101and at least one graphics processing unit. In another of theseembodiments, the computing device 100 includes at least one parallelprocessing unit and at least one graphics processing unit. In stillanother of these embodiments, the computing device 100 includes aplurality of processing units of any type, one of the plurality ofprocessing units comprising a graphics processing unit.

In some embodiments, a first computing device 100 a executes anapplication on behalf of a user of a client computing device 100 b. Inother embodiments, a computing device 100 a executes a virtual machine,which provides an execution session within which applications execute onbehalf of a user or a client computing devices 100 b. In one of theseembodiments, the execution session is a hosted desktop session. Inanother of these embodiments, the computing device 100 executes aterminal services session. The terminal services session may provide ahosted desktop environment. In still another of these embodiments, theexecution session provides access to a computing environment, which maycomprise one or more of: an application, a plurality of applications, adesktop application, and a desktop session in which one or moreapplications may execute.

B. Appliance Architecture

FIG. 2A illustrates an example embodiment of the appliance 200. Thearchitecture of the appliance 200 in FIG. 2A is provided by way ofillustration only and is not intended to be limiting. As shown in FIG.2, appliance 200 comprises a hardware layer 206 and a software layerdivided into a user space 202 and a kernel space 204.

Hardware layer 206 provides the hardware elements upon which programsand services within kernel space 204 and user space 202 are executed.Hardware layer 206 also provides the structures and elements which allowprograms and services within kernel space 204 and user space 202 tocommunicate data both internally and externally with respect toappliance 200. As shown in FIG. 2, the hardware layer 206 includes aprocessing unit 262 for executing software programs and services, amemory 264 for storing software and data, network ports 266 fortransmitting and receiving data over a network, and an encryptionprocessor 260 for performing functions related to Secure Sockets Layerprocessing of data transmitted and received over the network. In someembodiments, the central processing unit 262 may perform the functionsof the encryption processor 260 in a single processor. Additionally, thehardware layer 206 may comprise multiple processors for each of theprocessing unit 262 and the encryption processor 260. The processor 262may include any of the processors 101 described above in connection withFIGS. 1E and 1F. For example, in one embodiment, the appliance 200comprises a first processor 262 and a second processor 262′. In otherembodiments, the processor 262 or 262′ comprises a multi-core processor.

Although the hardware layer 206 of appliance 200 is generallyillustrated with an encryption processor 260, processor 260 may be aprocessor for performing functions related to any encryption protocol,such as the Secure Socket Layer (SSL) or Transport Layer Security (TLS)protocol. In some embodiments, the processor 260 may be a generalpurpose processor (GPP), and in further embodiments, may have executableinstructions for performing processing of any security related protocol.

Although the hardware layer 206 of appliance 200 is illustrated withcertain elements in FIG. 2, the hardware portions or components ofappliance 200 may comprise any type and form of elements, hardware orsoftware, of a computing device, such as the computing device 100illustrated and discussed herein in conjunction with FIGS. 1E and 1F. Insome embodiments, the appliance 200 may comprise a server, gateway,router, switch, bridge or other type of computing or network device, andhave any hardware and/or software elements associated therewith.

The operating system of appliance 200 allocates, manages, or otherwisesegregates the available system memory into kernel space 204 and userspace 204. In example software architecture 200, the operating systemmay be any type and/or form of Unix operating system although theinvention is not so limited. As such, the appliance 200 can be runningany operating system such as any of the versions of the Microsoft®Windows operating systems, the different releases of the Unix and Linuxoperating systems, any version of the Mac OS® for Macintosh computers,any embedded operating system, any network operating system, anyreal-time operating system, any open source operating system, anyproprietary operating system, any operating systems for mobile computingdevices or network devices, or any other operating system capable ofrunning on the appliance 200 and performing the operations describedherein.

The kernel space 204 is reserved for running the kernel 230, includingany device drivers, kernel extensions or other kernel related software.As known to those skilled in the art, the kernel 230 is the core of theoperating system, and provides access, control, and management ofresources and hardware-related elements of the application 104. Inaccordance with an embodiment of the appliance 200, the kernel space 204also includes a number of network services or processes working inconjunction with a cache manager 232, sometimes also referred to as theintegrated cache, the benefits of which are described in detail furtherherein. Additionally, the embodiment of the kernel 230 will depend onthe embodiment of the operating system installed, configured, orotherwise used by the device 200.

In one embodiment, the device 200 comprises one network stack 267, suchas a TCP/IP based stack, for communicating with the client 102 and/orthe server 106. In one embodiment, the network stack 267 is used tocommunicate with a first network, such as network 108, and a secondnetwork 110. In some embodiments, the device 200 terminates a firsttransport layer connection, such as a TCP connection of a client 102,and establishes a second transport layer connection to a server 106 foruse by the client 102, e.g., the second transport layer connection isterminated at the appliance 200 and the server 106. The first and secondtransport layer connections may be established via a single networkstack 267. In other embodiments, the device 200 may comprise multiplenetwork stacks, for example 267 and 267′, and the first transport layerconnection may be established or terminated at one network stack 267,and the second transport layer connection on the second network stack267′. For example, one network, stack may be for receiving andtransmitting network packet on a first network, and another networkstack for receiving and transmitting network packets on a secondnetwork. In one embodiment, the network stack 267 comprises a buffer 243for queuing one or more network packets for transmission by theappliance 200.

As shown in FIG. 2, the kernel space 204 includes the cache manager 232,a high-speed layer 2-7 integrated packet engine 240, an encryptionengine 234, a policy engine 236 and multi-protocol compression logic238. Running these components or processes 232, 240, 234, 236 and 238 inkernel space 204 or kernel mode instead of the user space 202 improvesthe performance of each of these components, alone and in combination.Kernel operation means that these components or processes 232, 240, 234,236 and 238 run in the core address space of the operating system of thedevice 200. For example, running the encryption engine 234 in kernelmode improves encryption performance by moving encryption and decryptionoperations to the kernel, thereby reducing the number of transitionsbetween the memory space or a kernel thread in kernel mode and thememory space or a thread in user mode. For example, data obtained inkernel mode may not need to be passed or copied to a process or threadrunning in user mode, such as from a kernel level data structure to auser level data structure. In another aspect, the number of contextswitches between kernel mode and user mode are also reduced.Additionally, synchronization of and communications between any of thecomponents or processes 232, 240, 235, 236 and 238 can be performed moreefficiently in the kernel space 204.

In some embodiments, any portion of the components 232, 240, 234, 236and 238 may run or operate in the kernel space 204, while other portionsof these components 232, 240, 234, 236 and 238 may run or operate inuser space 202. In one embodiment, the appliance 200 uses a kernel-leveldata structure providing access to any portion of one or more networkpackets, for example, a network packet comprising a request from aclient 102 or a response from a server 106. In some embodiments, thekernel-level data structure may be obtained by the packet engine 240 viaa transport layer driver interface or filter to the network stack 267.The kernel-level data structure may comprise any interface and/or dataaccessible via the kernel space 204 related to the network stack 267,network traffic or packets received or transmitted by the network stack267. In other embodiments, the kernel-level data structure may be usedby any of the components or processes 232, 240, 234, 236 and 238 toperform the desired operation of the component or process. In oneembodiment, a component 232, 240, 234, 236 and 238 is running in kernelmode 204 when using the kernel-level data structure, while in anotherembodiment, the component 232, 240, 234, 236 and 238 is running in usermode when using the kernel-level data structure. In some embodiments,the kernel-level data structure may be copied or passed to a secondkernel-level data structure, or any desired user-level data structure.

The cache manager 232 may comprise software, hardware or any combinationof software and hardware to provide cache access, control and managementof any type and form of content, such as objects or dynamicallygenerated objects served by the originating servers 106. The data,objects or content processed and stored by the cache manager 232 maycomprise data in any format, such as a markup language, or communicatedvia any protocol. In some embodiments, the cache manager 232 duplicatesoriginal data stored elsewhere or data previously computed, generated ortransmitted, in which the original data may require longer access timeto fetch, compute or otherwise obtain relative to reading a cache memoryelement. Once the data is stored in the cache memory element, future usecan be made by accessing the cached copy rather than refetching orrecomputing the original data, thereby reducing the access time. In someembodiments, the cache memory element may comprise a data object inmemory 264 of device 200. In other embodiments, the cache memory elementmay comprise memory having a faster access time than memory 264. Inanother embodiment, the cache memory element may comprise any type andform of storage element of the device 200, such as a portion of a harddisk. In some embodiments, the processing unit 262 may provide cachememory for use by the cache manager 232. In yet further embodiments, thecache manager 232 may use any portion and combination of memory,storage, or the processing unit for caching data, objects, and othercontent.

Furthermore, the cache manager 232 includes any logic, functions, rules,or operations to perform any embodiments of the techniques of theappliance 200 described herein. For example, the cache manager 232includes logic or functionality to invalidate objects based on theexpiration of an invalidation time period or upon receipt of aninvalidation command from a client 102 or server 106. In someembodiments, the cache manager 232 may operate as a program, service,process or task executing in the kernel space 204, and in otherembodiments, in the user space 202. In one embodiment, a first portionof the cache manager 232 executes in the user space 202 while a secondportion executes in the kernel space 204. In some embodiments, the cachemanager 232 can comprise any type of general purpose processor (GPP), orany other type of integrated circuit, such as a Field Programmable GateArray (FPGA), Programmable Logic Device (PLD), or Application SpecificIntegrated Circuit (ASIC).

The policy engine 236 may include, for example, an intelligentstatistical engine or other programmable application(s). In oneembodiment, the policy engine 236 provides a configuration mechanism toallow a user to identify, specify, define or configure a caching policy.Policy engine 236, in some embodiments, also has access to memory tosupport data structures such as lookup tables or hash tables to enableuser-selected caching policy decisions. In other embodiments, the policyengine 236 may comprise any logic, rules, functions or operations todetermine and provide access, control and management of objects, data orcontent being cached by the appliance 200 in addition to access, controland management of security, network traffic, network access, compressionor any other function or operation performed by the appliance 200.Further examples of specific caching policies are further describedherein.

The encryption engine 234 comprises any logic, business rules, functionsor operations for handling the processing of any security relatedprotocol, such as SSL or TLS, or any function related thereto. Forexample, the encryption engine 234 encrypts and decrypts networkpackets, or any portion thereof, communicated via the appliance 200. Theencryption engine 234 may also setup or establish SSL or TLS connectionson behalf of the client 102 a-102 n, server 106 a-106 n, or appliance200. As such, the encryption engine 234 provides offloading andacceleration of SSL processing. In one embodiment, the encryption engine234 uses a tunneling protocol to provide a virtual private networkbetween a client 102 a-102 n and a server 106 a-106 n. In someembodiments, the encryption engine 234 is in communication with theEncryption processor 260. In other embodiments, the encryption engine234 comprises executable instructions running on the Encryptionprocessor 260.

The multi-protocol compression engine 238 comprises any logic, businessrules, function or operations for compressing one or more protocols of anetwork packet, such as any of the protocols used by the network stack267 of the device 200. In one embodiment, multi-protocol compressionengine 238 compresses bi-directionally between clients 102 a-102 n andservers 106 a-106 n any TCP/IP based protocol, including MessagingApplication Programming Interface (MAPI) (email), File Transfer Protocol(FTP), HyperText Transfer Protocol (HTTP), Common Internet File System(CIFS) protocol (file transfer), Independent Computing Architecture(ICA) protocol, Remote Desktop Protocol (RDP), Wireless ApplicationProtocol (WAP), Mobile IP protocol, and Voice Over IP (VoIP) protocol.In other embodiments, multi-protocol compression engine 238 providescompression of Hypertext Markup Language (HTML) based protocols and insome embodiments, provides compression of any markup languages, such asthe Extensible Markup Language (XML). In one embodiment, themulti-protocol compression engine 238 provides compression of anyhigh-performance protocol, such as any protocol designed for appliance200 to appliance 200 communications. In another embodiment, themulti-protocol compression engine 238 compresses any payload of or anycommunication using a modified transport control protocol, such asTransaction TCP (T/TCP), TCP with selection acknowledgements (TCP-SACK),TCP with large windows (TCP-LW), a congestion prediction protocol suchas the TCP-Vegas protocol, and a TCP spoofing protocol.

As such, the multi-protocol compression engine 238 acceleratesperformance for users accessing applications via desktop clients, e.g.,Microsoft Outlook and non-Web thin clients, such as any client launchedby popular enterprise applications like Oracle, SAP and Siebel, and evenmobile clients, such as the Pocket PC. In some embodiments, themulti-protocol compression engine 238 by executing in the kernel mode204 and integrating with packet processing engine 240 accessing thenetwork stack 267 is able to compress any of the protocols carried bythe TCP/IP protocol, such as any application layer protocol.

High speed layer 2-7 integrated packet engine 240, also generallyreferred to as a packet processing engine or packet engine, isresponsible for managing the kernel-level processing of packets receivedand transmitted by appliance 200 via network ports 266. The high speedlayer 2-7 integrated packet engine 240 may comprise a buffer for queuingone or more network packets during processing, such as for receipt of anetwork packet or transmission of a network packet. Additionally, thehigh speed layer 2-7 integrated packet engine 240 is in communicationwith one or more network stacks 267 to send and receive network packetsvia network ports 266. The high speed layer 2-7 integrated packet engine240 works in conjunction with encryption engine 234, cache manager 232,policy engine 236 and multi-protocol compression logic 238. Inparticular, encryption engine 234 is configured to perform SSLprocessing of packets, policy engine 236 is configured to performfunctions related to traffic management such as request-level contentswitching and request-level cache redirection, and multi-protocolcompression logic 238 is configured to perform functions related tocompression and decompression of data.

The high speed layer 2-7 integrated packet engine 240 includes a packetprocessing timer 242. In one embodiment, the packet processing timer 242provides one or more time intervals to trigger the processing ofincoming, i.e., received, or outgoing, i.e., transmitted, networkpackets. In some embodiments, the high speed layer 2-7 integrated packetengine 240 processes network packets responsive to the timer 242. Thepacket processing timer 242 provides any type and form of signal to thepacket engine 240 to notify, trigger, or communicate a time relatedevent, interval or occurrence. In many embodiments, the packetprocessing timer 242 operates in the order of milliseconds, such as forexample 100 ms, 50 ms or 25 ms. For example, in some embodiments, thepacket processing timer 242 provides time intervals or otherwise causesa network packet to be processed by the high speed layer 2-7 integratedpacket engine 240 at a 10 ms time interval, while in other embodiments,at a 5 ms time interval, and still yet in further embodiments, as shortas a 3, 2, or 1 ms time interval. The high speed layer 2-7 integratedpacket engine 240 may be interfaced, integrated or in communication withthe encryption engine 234, cache manager 232, policy engine 236 andmulti-protocol compression engine 238 during operation. As such, any ofthe logic, functions, or operations of the encryption engine 234, cachemanager 232, policy engine 236 and multi-protocol compression logic 238may be performed responsive to the packet processing timer 242 and/orthe packet engine 240. Therefore, any of the logic, functions, oroperations of the encryption engine 234, cache manager 232, policyengine 236 and multi-protocol compression logic 238 may be performed atthe granularity of time intervals provided via the packet processingtimer 242, for example, at a time interval of less than or equal to 10ms. For example, in one embodiment, the cache manager 232 may performinvalidation of any cached objects responsive to the high speed layer2-7 integrated packet engine 240 and/or the packet processing timer 242.In another embodiment, the expiry or invalidation time of a cachedobject can be set to the same order of granularity as the time intervalof the packet processing timer 242, such as at every 10 ms.

In contrast to kernel space 204, user space 202 is the memory area orportion of the operating system used by user mode applications orprograms otherwise running in user mode. A user mode application may notaccess kernel space 204 directly and uses service calls in order toaccess kernel services. As shown in FIG. 2, user space 202 of appliance200 includes a graphical user interface (GUI) 210, a command lineinterface (CLI) 212, shell services 214, health monitoring program 216,and daemon services 218. GUI 210 and CLI 212 provide a means by which asystem administrator or other user can interact with and control theoperation of appliance 200, such as via the operating system of theappliance 200. The GUI 210 or CLI 212 can comprise code running in userspace 202 or kernel space 204. The GUI 210 may be any type and form ofgraphical user interface and may be presented via text, graphical orotherwise, by any type of program or application, such as a browser.The, CLI 212 may be any type and form of command line or text-basedinterface, such as a command line provided by the operating system. Forexample, the CLI 212 may comprise a shell, which is a tool to enableusers to interact with the operating system. In some embodiments, theCLI 212 may be provided via a bash, csh, tcsh, or ksh type shell. Theshell services 214 comprises the programs, services, tasks, processes orexecutable instructions to support interaction with the appliance 200 oroperating system by a user via the GUI 210 and/or CLI 212.

Health monitoring program 216 is used to monitor, check, report andensure that network systems are functioning properly and that users arereceiving requested content over a network. Health monitoring program216 comprises one or more programs, services, tasks, processes orexecutable instructions to provide logic, rules, functions or operationsfor monitoring any activity of the appliance 200. In some embodiments,the health monitoring program 216 intercepts and inspects any networktraffic passed via the appliance 200. In other embodiments, the healthmonitoring program 216 interfaces by any suitable means and/ormechanisms with one or more of the following: the encryption engine 234,cache manager 232, policy engine 236, multi-protocol compression logic238, packet engine 240, daemon services 218, and shell services 214. Assuch, the health monitoring program 216 may call any applicationprogramming interface (API) to determine a state, status, or health ofany portion of the appliance 200. For example, the health monitoringprogram 216 may ping or send a status inquiry on a periodic basis tocheck if a program, process, service or task is active and currentlyrunning. In another example, the health monitoring program 216 may checkany status, error or history logs provided by any program, process,service or task to determine any condition, status or error with anyportion of the appliance 200.

Daemon services 218 are programs that run continuously or in thebackground and handle periodic service requests received by appliance200. In some embodiments, a daemon service may forward the requests toother programs or processes, such as another daemon service 218 asappropriate. As known to those skilled in the art, a daemon service 218may run unattended to perform continuous or periodic system widefunctions, such as network control, or to perform any desired task. Insome embodiments, one or more daemon services 218 run in the user space202, while in other embodiments, one or more daemon services 218 run inthe kernel space.

Referring now to FIG. 2B, another embodiment of the appliance 200 isdepicted. In brief overview, the appliance 200 provides one or more ofthe following services, functionality or operations: SSL VPNconnectivity 280, switching/load balancing 284, Domain Name Serviceresolution 286, acceleration 288 and an application firewall 290 forcommunications between one or more clients 102 and one or more servers106. Each of the servers 106 may provide one or more network relatedservices 270 a-270 n (referred to as services 270). For example, aserver 106 may provide an http service 270. The appliance 200 comprisesone or more virtual servers or virtual internet protocol servers,referred to as a vServer, VIP server, or just VIP 275 a-275 n (alsoreferred herein as vServer 275). The vServer 275 receives, intercepts orotherwise processes communications between a client 102 and a server 106in accordance with the configuration and operations of the appliance200.

The vServer 275 may comprise software, hardware or any combination ofsoftware and hardware. The vServer 275 may comprise any type and form ofprogram, service, task, process or executable instructions operating inuser mode 202, kernel mode 204 or any combination thereof in theappliance 200. The vServer 275 includes any logic, functions, rules, oroperations to perform any embodiments of the techniques describedherein, such as SSL VPN 280, switching/load balancing 284, Domain NameService resolution 286, acceleration 288 and an application firewall290. In some embodiments, the vServer 275 establishes a connection to aservice 270 of a server 106. The service 275 may comprise any program,application, process, task or set of executable instructions capable ofconnecting to and communicating to the appliance 200, client 102 orvServer 275. For example, the service 275 may comprise a web server,http server, ftp, email or database server. In some embodiments, theservice 270 is a daemon process or network driver for listening,receiving and/or sending communications for an application, such asemail, database or an enterprise application. In some embodiments, theservice 270 may communicate on a specific IP address, or IP address andport.

In some embodiments, the vServer 275 applies one or more policies of thepolicy engine 236 to network communications between the client 102 andserver 106. In one embodiment, the policies are associated with avServer 275. In another embodiment, the policies are based on a user, ora group of users. In yet another embodiment, a policy is global andapplies to one or more vServers 275 a-275 n, and any user or group ofusers communicating via the appliance 200. In some embodiments, thepolicies of the policy engine have conditions upon which the policy isapplied based on any content of the communication, such as internetprotocol address, port, protocol type, header or fields in a packet, orthe context of the communication, such as user, group of the user,vServer 275, transport layer connection, and/or identification orattributes of the client 102 or server 106.

In other embodiments, the appliance 200 communicates or interfaces withthe policy engine 236 to determine authentication and/or authorizationof a remote user or a remote client 102 to access the computingenvironment 15, application, and/or data file from a server 106. Inanother embodiment, the appliance 200 communicates or interfaces withthe policy engine 236 to determine authentication and/or authorizationof a remote user or a remote client 102 to have the application deliverysystem 190 deliver one or more of the computing environment 15,application, and/or data file. In yet another embodiment, the appliance200 establishes a VPN or SSL VPN connection based on the policy engine's236 authentication and/or authorization of a remote user or a remoteclient 102 In one embodiment, the appliance 200 controls the flow ofnetwork traffic and communication sessions based on policies of thepolicy engine 236. For example, the appliance 200 may control the accessto a computing environment 15, application or data file based on thepolicy engine 236.

In some embodiments, the vServer 275 establishes a transport layerconnection, such as a TCP or UDP connection with a client 102 via theclient agent 120. In one embodiment, the vServer 275 listens for andreceives communications from the client 102. In other embodiments, thevServer 275 establishes a transport layer connection, such as a TCP orUDP connection with a client server 106. In one embodiment, the vServer275 establishes the transport layer connection to an internet protocoladdress and port of a server 270 running on the server 106. In anotherembodiment, the vServer 275 associates a first transport layerconnection to a client 102 with a second transport layer connection tothe server 106. In some embodiments, a vServer 275 establishes a pool oftransport layer connections to a server 106 and multiplexes clientrequests via the pooled transport layer connections.

In some embodiments, the appliance 200 provides a SSL VPN connection 280between a client 102 and a server 106. For example, a client 102 on afirst network 102 requests to establish a connection to a server 106 ona second network 104′. In some embodiments, the second network 104′ isnot routable from the first network 104. In other embodiments, theclient 102 is on a public network 104 and the server 106 is on a privatenetwork 104′, such as a corporate network. In one embodiment, the clientagent 120 intercepts communications of the client 102 on the firstnetwork 104, encrypts the communications, and transmits thecommunications via a first transport layer connection to the appliance200. The appliance 200 associates the first transport layer connectionon the first network 104 to a second transport layer connection to theserver 106 on the second network 104. The appliance 200 receives theintercepted communication from the client agent 102, decrypts thecommunications, and transmits the communication to the server 106 on thesecond network 104 via the second transport layer connection. The secondtransport layer connection may be a pooled transport layer connection.As such, the appliance 200 provides an end-to-end secure transport layerconnection for the client 102 between the two networks 104, 104′.

In one embodiment, the appliance 200 hosts an intranet internet protocolor IntranetIP 282 address of the client 102 on the virtual privatenetwork 104. The client 102 has a local network identifier, such as aninternet protocol (IP) address and/or host name on the first network104. When connected to the second network 104′ via the appliance 200,the appliance 200 establishes, assigns or otherwise provides anIntranetIP address 282, which is a network identifier, such as IPaddress and/or host name, for the client 102 on the second network 104′.The appliance 200 listens for and receives on the second or privatenetwork 104′ for any communications directed towards the client 102using the client's established IntranetIP 282. In one embodiment, theappliance 200 acts as or on behalf of the client 102 on the secondprivate network 104. For example, in another embodiment, a vServer 275listens for and responds to communications to the IntranetIP 282 of theclient 102. In some embodiments, if a computing device 100 on the secondnetwork 104′ transmits a request, the appliance 200 processes therequest as if it were the client 102. For example, the appliance 200 mayrespond to a ping to the client's IntranetIP 282. In another example,the appliance may establish a connection, such as a TCP or UDPconnection, with computing device 100 on the second network 104requesting a connection with the client's IntranetIP 282.

In some embodiments, the appliance 200 provides one or more of thefollowing acceleration techniques 288 to communications between theclient 102 and server 106: 1) compression; 2) decompression; 3)Transmission Control Protocol pooling; 4) Transmission Control Protocolmultiplexing; 5) Transmission Control Protocol buffering; and 6)caching. In one embodiment, the appliance 200 relieves servers 106 ofmuch of the processing load caused by repeatedly opening and closingtransport layers connections to clients 102 by opening one or moretransport layer connections with each server 106 and maintaining theseconnections to allow repeated data accesses by clients via the Internet.This technique is referred to herein as “connection pooling”.

In some embodiments, in order to seamlessly splice communications from aclient 102 to a server 106 via a pooled transport layer connection, theappliance 200 translates or multiplexes communications by modifyingsequence number and acknowledgment numbers at the transport layerprotocol level. This is referred to as “connection multiplexing”. Insome embodiments, no application layer protocol interaction is required.For example, in the case of an in-bound packet (that is, a packetreceived from a client 102), the source network address of the packet ischanged to that of an output port of appliance 200, and the destinationnetwork address is changed to that of the intended server. In the caseof an outbound packet (that is, one received from a server 106), thesource network address is changed from that of the server 106 to that ofan output port of appliance 200 and the destination address is changedfrom that of appliance 200 to that of the requesting client 102. Thesequence numbers and acknowledgment numbers of the packet are alsotranslated to sequence numbers and acknowledgement numbers expected bythe client 102 on the appliance's 200 transport layer connection to theclient 102. In some embodiments, the packet checksum of the transportlayer protocol is recalculated to account for these translations.

In another embodiment, the appliance 200 provides switching orload-balancing functionality 284 for communications between the client102 and server 106. In some embodiments, the appliance 200 distributestraffic and directs client requests to a server 106 based on layer 4 orapplication-layer request data. In one embodiment, although the networklayer or layer 2 of the network packet identifies a destination server106, the appliance 200 determines the server 106 to distribute thenetwork packet by application information and data carried as payload ofthe transport layer packet. In one embodiment, the health monitoringprograms 216 of the appliance 200 monitor the health of servers todetermine the server 106 for which to distribute a client's request. Insome embodiments, if the appliance 200 detects a server 106 is notavailable or has a load over a predetermined threshold, the appliance200 can direct or distribute client requests to another server 106.

In some embodiments, the appliance 200 acts as a Domain Name Service(DNS) resolver or otherwise provides resolution of a DNS request fromclients 102. In some embodiments, the appliance intercepts a DNS requesttransmitted by the client 102. In one embodiment, the appliance 200responds to a client's DNS request with an IP address of or hosted bythe appliance 200. In this embodiment, the client 102 transmits networkcommunication for the domain name to the appliance 200. In anotherembodiment, the appliance 200 responds to a client's DNS request with anIP address of or hosted by a second appliance 200′. In some embodiments,the appliance 200 responds to a client's DNS request with an IP addressof a server 106 determined by the appliance 200.

In yet another embodiment, the appliance 200 provides applicationfirewall functionality 290 for communications between the client 102 andserver 106. In one embodiment, the policy engine 236 provides rules fordetecting and blocking illegitimate requests. In some embodiments, theapplication firewall 290 protects against denial of service (DoS)attacks. In other embodiments, the appliance inspects the content ofintercepted requests to identify and block application-based attacks. Insome embodiments, the rules/policy engine 236 comprises one or moreapplication firewall or security control policies for providingprotections against various classes and types of web or Internet basedvulnerabilities, such as one or more of the following: 1) bufferoverflow, 2) CGI-BIN parameter manipulation, 3) form/hidden fieldmanipulation, 4) forceful browsing, 5) cookie or session poisoning, 6)broken access control list (ACLs) or weak passwords, 7) cross-sitescripting (XSS), 8) command injection, 9) SQL injection, 10) errortriggering sensitive information leak, 11) insecure use of cryptography,12) server misconfiguration, 13) back doors and debug options, 14)website defacement, 15) platform or operating systems vulnerabilities,and 16) zero-day exploits. In an embodiment, the application firewall290 provides HTML form field protection in the form of inspecting oranalyzing the network communication for one or more of the following: 1)required fields are returned, 2) no added field allowed, 3) read-onlyand hidden field enforcement, 4) drop-down list and radio button fieldconformance, and 5) form-field max-length enforcement. In someembodiments, the application firewall 290 ensures cookies are notmodified. In other embodiments, the application firewall 290 protectsagainst forceful browsing by enforcing legal URLs.

In still yet other embodiments, the application firewall 290 protectsany confidential information contained in the network communication. Theapplication firewall 290 may inspect or analyze any networkcommunication in accordance with the rules or polices of the engine 236to identify any confidential information in any field of the networkpacket. In some embodiments, the application firewall 290 identifies inthe network communication one or more occurrences of a credit cardnumber, password, social security number, name, patient code, contactinformation, and age. The encoded portion of the network communicationmay comprise these occurrences or the confidential information. Based onthese occurrences, in one embodiment, the application firewall 290 maytake a policy action on the network communication, such as preventtransmission of the network communication. In another embodiment, theapplication firewall 290 may rewrite, remove or otherwise mask suchidentified occurrence or confidential information.

Still referring to FIG. 2B, the appliance 200 may include a performancemonitoring agent 197 as discussed above in conjunction with FIG. 1D. Inone embodiment, the appliance 200 receives the monitoring agent 197 fromthe monitoring service 198 or monitoring server 106 as depicted in FIG.1D. In some embodiments, the appliance 200 stores the monitoring agent197 in storage, such as disk, for delivery to any client or server incommunication with the appliance 200. For example, in one embodiment,the appliance 200 transmits the monitoring agent 197 to a client uponreceiving a request to establish a transport layer connection. In otherembodiments, the appliance 200 transmits the monitoring agent 197 uponestablishing the transport layer connection with the client 102. Inanother embodiment, the appliance 200 transmits the monitoring agent 197to the client upon intercepting or detecting a request for a web page.In yet another embodiment, the appliance 200 transmits the monitoringagent 197 to a client or a server in response to a request from themonitoring server 198. In one embodiment, the appliance 200 transmitsthe monitoring agent 197 to a second appliance 200′ or appliance 205.

In other embodiments, the appliance 200 executes the monitoring agent197. In one embodiment, the monitoring agent 197 measures and monitorsthe performance of any application, program, process, service, task orthread executing on the appliance 200. For example, the monitoring agent197 may monitor and measure performance and operation of vServers275A-275N. In another embodiment, the monitoring agent 197 measures andmonitors the performance of any transport layer connections of theappliance 200. In some embodiments, the monitoring agent 197 measuresand monitors the performance of any user sessions traversing theappliance 200. In one embodiment, the monitoring agent 197 measures andmonitors the performance of any virtual private network connectionsand/or sessions traversing the appliance 200, such as an SSL VPNsession. In still further embodiments, the monitoring agent 197 measuresand monitors the memory, CPU and disk usage and performance of theappliance 200. In yet another embodiment, the monitoring agent 197measures and monitors the performance of any acceleration technique 288performed by the appliance 200, such as SSL offloading, connectionpooling and multiplexing, caching, and compression. In some embodiments,the monitoring agent 197 measures and monitors the performance of anyload balancing and/or content switching 284 performed by the appliance200. In other embodiments, the monitoring agent 197 measures andmonitors the performance of application firewall 290 protection andprocessing performed by the appliance 200.

C. Client Agent

Referring now to FIG. 3, an embodiment of the client agent 120 isdepicted. The client 102 includes a client agent 120 for establishingand exchanging communications with the appliance 200 and/or server 106via a network 104. In brief overview, the client 102 operates oncomputing device 100 having an operating system with a kernel mode 302and a user mode 303, and a network stack 310 with one or more layers 310a-310 b. The client 102 may have installed and/or execute one or moreapplications. In some embodiments, one or more applications maycommunicate via the network stack 310 to a network 104. One of theapplications, such as a web browser, may also include a first program322. For example, the first program 322 may be used in some embodimentsto install and/or execute the client agent 120, or any portion thereof.The client agent 120 includes an interception mechanism, or interceptor350, for intercepting network communications from the network stack 310from the one or more applications.

The network stack 310 of the client 102 may comprise any type and formof software, or hardware, or any combinations thereof, for providingconnectivity to and communications with a network. In one embodiment,the network stack 310 comprises a software implementation for a networkprotocol suite. The network stack 310 may comprise one or more networklayers, such as any networks layers of the Open Systems Interconnection(OSI) communications model as those skilled in the art recognize andappreciate. As such, the network stack 310 may comprise any type andform of protocols for any of the following layers of the OSI model: 1)physical link layer, 2) data link layer, 3) network layer, 4) transportlayer, 5) session layer, 6) presentation layer, and 7) applicationlayer. In one embodiment, the network stack 310 may comprise a transportcontrol protocol (TCP) over the network layer protocol of the internetprotocol (IP), generally referred to as TCP/IP. In some embodiments, theTCP/IP protocol may be carried over the Ethernet protocol, which maycomprise any of the family of IEEE wide-area-network (WAN) orlocal-area-network (LAN) protocols, such as those protocols covered bythe IEEE 802.3. In some embodiments, the network stack 310 comprises anytype and form of a wireless protocol, such as IEEE 802.11 and/or mobileinternet protocol.

In view of a TCP/IP based network, any TCP/IP based protocol may beused, including Messaging Application Programming Interface (MAPI)(email), File Transfer Protocol (FTP), HyperText Transfer Protocol(HTTP), Common Internet File System (CIFS) protocol (file transfer),Independent Computing Architecture (ICA) protocol, Remote DesktopProtocol (RDP), Wireless Application Protocol (WAP), Mobile IP protocol,and Voice Over IP (VoIP) protocol. In another embodiment, the networkstack 310 comprises any type and form of transport control protocol,such as a modified transport control protocol, for example a TransactionTCP (T/TCP), TCP with selection acknowledgements (TCP-SACK), TCP withlarge windows (TCP-LW), a congestion prediction protocol such as theTCP-Vegas protocol, and a TCP spoofing protocol. In other embodiments,any type and form of user datagram protocol (UDP), such as UDP over IP,may be used by the network stack 310, such as for voice communicationsor real-time data communications.

Furthermore, the network stack 310 may include one or more networkdrivers supporting the one or more layers, such as a TCP driver or anetwork layer driver. The network drivers may be included as part of theoperating system of the computing device 100 or as part of any networkinterface cards or other network access components of the computingdevice 100. In some embodiments, any of the network drivers of thenetwork stack 310 may be customized, modified or adapted to provide acustom or modified portion of the network stack 310 in support of any ofthe techniques described herein. In other embodiments, the accelerationprogram 302 is designed and constructed to operate with or work inconjunction with the network stack 310 installed or otherwise providedby the operating system of the client 102.

The network stack 310 comprises any type and form of interfaces forreceiving, obtaining, providing or otherwise accessing any informationand data related to network communications of the client 102. In oneembodiment, an interface to the network stack 310 comprises anapplication programming interface (API). The interface may also compriseany function call, hooking or filtering mechanism, event or call backmechanism, or any type of interfacing technique. The network stack 310via the interface may receive or provide any type and form of datastructure, such as an object, related to functionality or operation ofthe network stack 310. For example, the data structure may compriseinformation and data related to a network packet or one or more networkpackets. In some embodiments, the data structure comprises a portion ofthe network packet processed at a protocol layer of the network stack310, such as a network packet of the transport layer. In someembodiments, the data structure 325 comprises a kernel-level datastructure, while in other embodiments, the data structure 325 comprisesa user-mode data structure. A kernel-level data structure may comprise adata structure obtained or related to a portion of the network stack 310operating in kernel-mode 302, or a network driver or other softwarerunning in kernel-mode 302, or any data structure obtained or receivedby a service, process, task, thread or other executable instructionsrunning or operating in kernel-mode of the operating system.

Additionally, some portions of the network stack 310 may execute oroperate in kernel-mode 302, for example, the data link or network layer,while other portions execute or operate in user-mode 303, such as anapplication layer of the network stack 310. For example, a first portion310 a of the network stack may provide user-mode access to the networkstack 310 to an application while a second portion 310 a of the networkstack 310 provides access to a network. In some embodiments, a firstportion 310 a of the network stack may comprise one or more upper layersof the network stack 310, such as any of layers 5-7. In otherembodiments, a second portion 310 b of the network stack 310 comprisesone or more lower layers, such as any of layers 1-4. Each of the firstportion 310 a and second portion 310 b of the network stack 310 maycomprise any portion of the network stack 310, at any one or morenetwork layers, in user-mode 203, kernel-mode, 202, or combinationsthereof, or at any portion of a network layer or interface point to anetwork layer or any portion of or interface point to the user-mode 203and kernel-mode 203.

The interceptor 350 may comprise software, hardware, or any combinationof software and hardware. In one embodiment, the interceptor 350intercept a network communication at any point in the network stack 310,and redirects or transmits the network communication to a destinationdesired, managed or controlled by the interceptor 350 or client agent120. For example, the interceptor 350 may intercept a networkcommunication of a network stack 310 of a first network and transmit thenetwork communication to the appliance 200 for transmission on a secondnetwork 104. In some embodiments, the interceptor 350 comprises any typeinterceptor 350 comprises a driver, such as a network driver constructedand designed to interface and work with the network stack 310. In someembodiments, the client agent 120 and/or interceptor 350 operates at oneor more layers of the network stack 310, such as at the transport layer.In one embodiment, the interceptor 350 comprises a filter driver,hooking mechanism, or any form and type of suitable network driverinterface that interfaces to the transport layer of the network stack,such as via the transport driver interface (TDI). In some embodiments,the interceptor 350 interfaces to a first protocol layer, such as thetransport layer and another protocol layer, such as any layer above thetransport protocol layer, for example, an application protocol layer. Inone embodiment, the interceptor 350 may comprise a driver complying withthe Network Driver Interface Specification (NDIS), or a NDIS driver. Inanother embodiment, the interceptor 350 may comprise a mini-filter or amini-port driver. In one embodiment, the interceptor 350, or portionthereof, operates in kernel-mode 202. In another embodiment, theinterceptor 350, or portion thereof, operates in user-mode 203. In someembodiments, a portion of the interceptor 350 operates in kernel-mode202 while another portion of the interceptor 350 operates in user-mode203. In other embodiments, the client agent 120 operates in user-mode203 but interfaces via the interceptor 350 to a kernel-mode driver,process, service, task or portion of the operating system, such as toobtain a kernel-level data structure 225. In further embodiments, theinterceptor 350 is a user-mode application or program, such asapplication.

In one embodiment, the interceptor 350 intercepts any transport layerconnection requests. In these embodiments, the interceptor 350 executetransport layer application programming interface (API) calls to set thedestination information, such as destination IP address and/or port to adesired location for the location. In this manner, the interceptor 350intercepts and redirects the transport layer connection to a IP addressand port controlled or managed by the interceptor 350 or client agent120. In one embodiment, the interceptor 350 sets the destinationinformation for the connection to a local IP address and port of theclient 102 on which the client agent 120 is listening. For example, theclient agent 120 may comprise a proxy service listening on a local IPaddress and port for redirected transport layer communications. In someembodiments, the client agent 120 then communicates the redirectedtransport layer communication to the appliance 200.

In some embodiments, the interceptor 350 intercepts a Domain NameService (DNS) request. In one embodiment, the client agent 120 and/orinterceptor 350 resolves the DNS request. In another embodiment, theinterceptor transmits the intercepted DNS request to the appliance 200for DNS resolution. In one embodiment, the appliance 200 resolves theDNS request and communicates the DNS response to the client agent 120.In some embodiments, the appliance 200 resolves the DNS request viaanother appliance 200′ or a DNS server 106.

In yet another embodiment, the client agent 120 may comprise two agents120 and 120′. In one embodiment, a first agent 120 may comprise aninterceptor 350 operating at the network layer of the network stack 310.In some embodiments, the first agent 120 intercepts network layerrequests such as Internet Control Message Protocol (ICMP) requests(e.g., ping and traceroute). In other embodiments, the second agent 120′may operate at the transport layer and intercept transport layercommunications. In some embodiments, the first agent 120 interceptscommunications at one layer of the network stack 210 and interfaces withor communicates the intercepted communication to the second agent 120′.

The client agent 120 and/or interceptor 350 may operate at or interfacewith a protocol layer in a manner transparent to any other protocollayer of the network stack 310. For example, in one embodiment, theinterceptor 350 operates or interfaces with the transport layer of thenetwork stack 310 transparently to any protocol layer below thetransport layer, such as the network layer, and any protocol layer abovethe transport layer, such as the session, presentation or applicationlayer protocols. This allows the other protocol layers of the networkstack 310 to operate as desired and without modification for using theinterceptor 350. As such, the client agent 120 and/or interceptor 350can interface with the transport layer to secure, optimize, accelerate,route or load-balance any communications provided via any protocolcarried by the transport layer, such as any application layer protocolover TCP/IP.

Furthermore, the client agent 120 and/or interceptor may operate at orinterface with the network stack 310 in a manner transparent to anyapplication, a user of the client 102, and any other computing device,such as a server, in communications with the client 102. The clientagent 120 and/or interceptor 350 may be installed and/or executed on theclient 102 in a manner without modification of an application. In someembodiments, the user of the client 102 or a computing device incommunications with the client 102 are not aware of the existence,execution or operation of the client agent 120 and/or interceptor 350.As such, in some embodiments, the client agent 120 and/or interceptor350 is installed, executed, and/or operated transparently to anapplication, user of the client 102, another computing device, such as aserver, or any of the protocol layers above and/or below the protocollayer interfaced to by the interceptor 350.

The client agent 120 includes an acceleration program 302, a streamingclient 306, a collection agent 304, and/or monitoring agent 197. In oneembodiment, the client agent 120 comprises an Independent ComputingArchitecture (ICA) client, or any portion thereof, developed by CitrixSystems, Inc. of Fort Lauderdale, Fla., and is also referred to as anICA client. In some embodiments, the client 120 comprises an applicationstreaming client 306 for streaming an application from a server 106 to aclient 102. In some embodiments, the client agent 120 comprises anacceleration program 302 for accelerating communications between client102 and server 106. In another embodiment, the client agent 120 includesa collection agent 304 for performing end-point detection/scanning andcollecting end-point information for the appliance 200 and/or server106.

In some embodiments, the acceleration program 302 comprises aclient-side acceleration program for performing one or more accelerationtechniques to accelerate, enhance or otherwise improve a client'scommunications with and/or access to a server 106, such as accessing anapplication provided by a server 106. The logic, functions, and/oroperations of the executable instructions of the acceleration program302 may perform one or more of the following acceleration techniques: 1)multi-protocol compression, 2) transport control protocol pooling, 3)transport control protocol multiplexing, 4) transport control protocolbuffering, and 5) caching via a cache manager. Additionally, theacceleration program 302 may perform encryption and/or decryption of anycommunications received and/or transmitted by the client 102. In someembodiments, the acceleration program 302 performs one or more of theacceleration techniques in an integrated manner or fashion.Additionally, the acceleration program 302 can perform compression onany of the protocols, or multiple-protocols, carried as a payload of anetwork packet of the transport layer protocol. The streaming client 306comprises an application, program, process, service, task or executableinstructions for receiving and executing a streamed application from aserver 106. A server 106 may stream one or more application data filesto the streaming client 306 for playing, executing or otherwise causingto be executed the application on the client 102. In some embodiments,the server 106 transmits a set of compressed or packaged applicationdata files to the streaming client 306. In some embodiments, theplurality of application files are compressed and stored on a fileserver within an archive file such as a CAB, ZIP, SIT, TAR, JAR or otherarchive. In one embodiment, the server 106 decompresses, unpackages orunarchives the application files and transmits the files to the client102. In another embodiment, the client 102 decompresses, unpackages orunarchives the application files. The streaming client 306 dynamicallyinstalls the application, or portion thereof, and executes theapplication. In one embodiment, the streaming client 306 may be anexecutable program. In some embodiments, the streaming client 306 may beable to launch another executable program.

The collection agent 304 comprises an application, program, process,service, task or executable instructions for identifying, obtainingand/or collecting information about the client 102. In some embodiments,the appliance 200 transmits the collection agent 304 to the client 102or client agent 120. The collection agent 304 may be configuredaccording to one or more policies of the policy engine 236 of theappliance. In other embodiments, the collection agent 304 transmitscollected information on the client 102 to the appliance 200. In oneembodiment, the policy engine 236 of the appliance 200 uses thecollected information to determine and provide access, authenticationand authorization control of the client's connection to a network 104.

In one embodiment, the collection agent 304 comprises an end-pointdetection and scanning mechanism, which identifies and determines one ormore attributes or characteristics of the client. For example, thecollection agent 304 may identify and determine any one or more of thefollowing client-side attributes: 1) the operating system an/or aversion of an operating system, 2) a service pack of the operatingsystem, 3) a running service, 4) a running process, and 5) a file. Thecollection agent 304 may also identify and determine the presence orversions of any one or more of the following on the client: 1) antivirussoftware, 2) personal firewall software, 3) anti-spam software, and 4)internet security software. The policy engine 236 may have one or morepolicies based on any one or more of the attributes or characteristicsof the client or client-side attributes.

In some embodiments, the client agent 120 includes a monitoring agent197 as discussed in conjunction with FIGS. 1D and 2B. The monitoringagent 197 may be any type and form of script, such as Visual Basic orJava script. In one embodiment, the monitoring agent 197 monitors andmeasures performance of any portion of the client agent 120. Forexample, in some embodiments, the monitoring agent 197 monitors andmeasures performance of the acceleration program 302. In anotherembodiment, the monitoring agent 197 monitors and measures performanceof the streaming client 306. In other embodiments, the monitoring agent197 monitors and measures performance of the collection agent 304. Instill another embodiment, the monitoring agent 197 monitors and measuresperformance of the interceptor 350. In some embodiments, the monitoringagent 197 monitors and measures any resource of the client 102, such asmemory, CPU and disk.

The monitoring agent 197 may monitor and measure performance of anyapplication of the client. In one embodiment, the monitoring agent 197monitors and measures performance of a browser on the client 102. Insome embodiments, the monitoring agent 197 monitors and measuresperformance of any application delivered via the client agent 120. Inother embodiments, the monitoring agent 197 measures and monitors enduser response times for an application, such as web-based or HTTPresponse times. The monitoring agent 197 may monitor and measureperformance of an ICA or RDP client. In another embodiment, themonitoring agent 197 measures and monitors metrics for a user session orapplication session. In some embodiments, monitoring agent 197 measuresand monitors an ICA or RDP session. In one embodiment, the monitoringagent 197 measures and monitors the performance of the appliance 200 inaccelerating delivery of an application and/or data to the client 102.

In some embodiments and still referring to FIG. 3, a first program 322may be used to install and/or execute the client agent 120, or portionthereof, such as the interceptor 350, automatically, silently,transparently, or otherwise. In one embodiment, the first program 322comprises a plugin component, such an ActiveX control or Java control orscript that is loaded into and executed by an application. For example,the first program comprises an ActiveX control loaded and run by a webbrowser application, such as in the memory space or context of theapplication. In another embodiment, the first program 322 comprises aset of executable instructions loaded into and run by the application,such as a browser. In one embodiment, the first program 322 comprises adesigned and constructed program to install the client agent 120. Insome embodiments, the first program 322 obtains, downloads, or receivesthe client agent 120 via the network from another computing device. Inanother embodiment, the first program 322 is an installer program or aplug and play manager for installing programs, such as network drivers,on the operating system of the client 102.

D. Systems and Methods for Providing Virtualized Application DeliveryController

Referring now to FIG. 4A, a block diagram depicts one embodiment of avirtualization environment 400. In brief overview, a computing device100 includes a hypervisor layer, a virtualization layer, and a hardwarelayer. The hypervisor layer includes a hypervisor 401 (also referred toas a virtualization manager) that allocates and manages access to anumber of physical resources in the hardware layer (e.g., theprocessor(s) 421, and disk(s) 428) by at least one virtual machineexecuting in the virtualization layer. The virtualization layer includesat least one operating system 410 and a plurality of virtual resourcesallocated to the at least one operating system 410. Virtual resourcesmay include, without limitation, a plurality of virtual processors 432a, 432 b, 432 c (generally 432), and virtual disks 442 a, 442 b, 442 c(generally 442), as well as virtual resources such as virtual memory andvirtual network interfaces. The plurality of virtual resources and theoperating system 410 may be referred to as a virtual machine 406. Avirtual machine 406 may include a control operating system 405 incommunication with the hypervisor 401 and used to execute applicationsfor managing and configuring other virtual machines on the computingdevice 100.

In greater detail, a hypervisor 401 may provide virtual resources to anoperating system in any manner which simulates the operating systemhaving access to a physical device. A hypervisor 401 may provide virtualresources to any number of guest operating systems 410 a, 410 b(generally 410). In some embodiments, a computing device 100 executesone or more types of hypervisors. In these embodiments, hypervisors maybe used to emulate virtual hardware, partition physical hardware,virtualize physical hardware, and execute virtual machines that provideaccess to computing environments. Hypervisors may include thosemanufactured by VMWare, Inc., of Palo Alto, Calif.; the XEN hypervisor,an open source product whose development is overseen by the open sourceXen.org community; HyperV, VirtualServer or virtual PC hypervisorsprovided by Microsoft, or others. In some embodiments, a computingdevice 100 executing a hypervisor that creates a virtual machineplatform on which guest operating systems may execute is referred to asa host server. In one of these embodiments, for example, the computingdevice 100 is a XEN SERVER provided by Citrix Systems, Inc., of FortLauderdale, Fla.

In some embodiments, a hypervisor 401 executes within an operatingsystem executing on a computing device. In one of these embodiments, acomputing device executing an operating system and a hypervisor 401 maybe said to have a host operating system (the operating system executingon the computing device), and a guest operating system (an operatingsystem executing within a computing resource partition provided by thehypervisor 401). In other embodiments, a hypervisor 401 interactsdirectly with hardware on a computing device, instead of executing on ahost operating system. In one of these embodiments, the hypervisor 401may be said to be executing on “bare metal,” referring to the hardwarecomprising the computing device.

In some embodiments, a hypervisor 401 may create a virtual machine 406a-c (generally 406) in which an operating system 410 executes. In one ofthese embodiments, for example, the hypervisor 401 loads a virtualmachine image to create a virtual machine 406. In another of theseembodiments, the hypervisor 401 executes an operating system 410 withinthe virtual machine 406. In still another of these embodiments, thevirtual machine 406 executes an operating system 410.

In some embodiments, the hypervisor 401 controls processor schedulingand memory partitioning for a virtual machine 406 executing on thecomputing device 100. In one of these embodiments, the hypervisor 401controls the execution of at least one virtual machine 406. In anotherof these embodiments, the hypervisor 401 presents at least one virtualmachine 406 with an abstraction of at least one hardware resourceprovided by the computing device 100. In other embodiments, thehypervisor 401 controls whether and how physical processor capabilitiesare presented to the virtual machine 406.

A control operating system 405 may execute at least one application formanaging and configuring the guest operating systems. In one embodiment,the control operating system 405 may execute an administrativeapplication, such as an application including a user interface providingadministrators with access to functionality for managing the executionof a virtual machine, including functionality for executing a virtualmachine, terminating an execution of a virtual machine, or identifying atype of physical resource for allocation to the virtual machine. Inanother embodiment, the hypervisor 401 executes the control operatingsystem 405 within a virtual machine 406 created by the hypervisor 401.In still another embodiment, the control operating system 405 executesin a virtual machine 406 that is authorized to directly access physicalresources on the computing device 100. In some embodiments, a controloperating system 405 a on a computing device 100 a may exchange datawith a control operating system 405 b on a computing device 100 b, viacommunications between a hypervisor 401 a and a hypervisor 401 b. Inthis way, one or more computing devices 100 may exchange data with oneor more of the other computing devices 100 regarding processors andother physical resources available in a pool of resources. In one ofthese embodiments, this functionality allows a hypervisor to manage apool of resources distributed across a plurality of physical computingdevices. In another of these embodiments, multiple hypervisors manageone or more of the guest operating systems executed on one of thecomputing devices 100.

In one embodiment, the control operating system 405 executes in avirtual machine 406 that is authorized to interact with at least oneguest operating system 410. In another embodiment, a guest operatingsystem 410 communicates with the control operating system 405 via thehypervisor 401 in order to request access to a disk or a network. Instill another embodiment, the guest operating system 410 and the controloperating system 405 may communicate via a communication channelestablished by the hypervisor 401, such as, for example, via a pluralityof shared memory pages made available by the hypervisor 401.

In some embodiments, the control operating system 405 includes a networkback-end driver for communicating directly with networking hardwareprovided by the computing device 100. In one of these embodiments, thenetwork back-end driver processes at least one virtual machine requestfrom at least one guest operating system 110. In other embodiments, thecontrol operating system 405 includes a block back-end driver forcommunicating with a storage element on the computing device 100. In oneof these embodiments, the block back-end driver reads and writes datafrom the storage element based upon at least one request received from aguest operating system 410.

In one embodiment, the control operating system 405 includes a toolsstack 404. In another embodiment, a tools stack 404 providesfunctionality for interacting with the hypervisor 401, communicatingwith other control operating systems 405 (for example, on a secondcomputing device 100 b), or managing virtual machines 406 b, 406 c onthe computing device 100. In another embodiment, the tools stack 404includes customized applications for providing improved managementfunctionality to an administrator of a virtual machine farm. In someembodiments, at least one of the tools stack 404 and the controloperating system 405 include a management API that provides an interfacefor remotely configuring and controlling virtual machines 406 running ona computing device 100. In other embodiments, the control operatingsystem 405 communicates with the hypervisor 401 through the tools stack404.

In one embodiment, the hypervisor 401 executes a guest operating system410 within a virtual machine 406 created by the hypervisor 401. Inanother embodiment, the guest operating system 410 provides a user ofthe computing device 100 with access to resources within a computingenvironment. In still another embodiment, a resource includes a program,an application, a document, a file, a plurality of applications, aplurality of files, an executable program file, a desktop environment, acomputing environment, or other resource made available to a user of thecomputing device 100. In yet another embodiment, the resource may bedelivered to the computing device 100 via a plurality of access methodsincluding, but not limited to, conventional installation directly on thecomputing device 100, delivery to the computing device 100 via a methodfor application streaming, delivery to the computing device 100 ofoutput data generated by an execution of the resource on a secondcomputing device 100′ and communicated to the computing device 100 via apresentation layer protocol, delivery to the computing device 100 ofoutput data generated by an execution of the resource via a virtualmachine executing on a second computing device 100′, or execution from aremovable storage device connected to the computing device 100, such asa USB device, or via a virtual machine executing on the computing device100 and generating output data. In some embodiments, the computingdevice 100 transmits output data generated by the execution of theresource to another computing device 100′.

In one embodiment, the guest operating system 410, in conjunction withthe virtual machine on which it executes, forms a fully-virtualizedvirtual machine which is not aware that it is a virtual machine; such amachine may be referred to as a “Domain U HVM (Hardware Virtual Machine)virtual machine”. In another embodiment, a fully-virtualized machineincludes software emulating a Basic Input/Output System (BIOS) in orderto execute an operating system within the fully-virtualized machine. Instill another embodiment, a fully-virtualized machine may include adriver that provides functionality by communicating with the hypervisor401. In such an embodiment, the driver may be aware that it executeswithin a virtualized environment. In another embodiment, the guestoperating system 410, in conjunction with the virtual machine on whichit executes, forms a paravirtualized virtual machine, which is awarethat it is a virtual machine; such a machine may be referred to as a“Domain U PV virtual machine”. In another embodiment, a paravirtualizedmachine includes additional drivers that a fully-virtualized machinedoes not include. In still another embodiment, the paravirtualizedmachine includes the network back-end driver and the block back-enddriver included in a control operating system 405, as described above.

Referring now to FIG. 4B, a block diagram depicts one embodiment of aplurality of networked computing devices in a system in which at leastone physical host executes a virtual machine. In brief overview, thesystem includes a management component 404 and a hypervisor 401. Thesystem includes a plurality of computing devices 100, a plurality ofvirtual machines 406, a plurality of hypervisors 401, a plurality ofmanagement components referred to variously as tools stacks 404 ormanagement components 404, and a physical resource 421, 428. Theplurality of physical machines 100 may each be provided as computingdevices 100, described above in connection with FIGS. 1E-1H and 4A.

In greater detail, a physical disk 428 is provided by a computing device100 and stores at least a portion of a virtual disk 442. In someembodiments, a virtual disk 442 is associated with a plurality ofphysical disks 428. In one of these embodiments, one or more computingdevices 100 may exchange data with one or more of the other computingdevices 100 regarding processors and other physical resources availablein a pool of resources, allowing a hypervisor to manage a pool ofresources distributed across a plurality of physical computing devices.In some embodiments, a computing device 100 on which a virtual machine406 executes is referred to as a physical host 100 or as a host machine100.

The hypervisor executes on a processor on the computing device 100. Thehypervisor allocates, to a virtual disk, an amount of access to thephysical disk. In one embodiment, the hypervisor 401 allocates an amountof space on the physical disk. In another embodiment, the hypervisor 401allocates a plurality of pages on the physical disk. In someembodiments, the hypervisor provisions the virtual disk 442 as part of aprocess of initializing and executing a virtual machine 450.

In one embodiment, the management component 404 a is referred to as apool management component 404 a. In another embodiment, a managementoperating system 405 a, which may be referred to as a control operatingsystem 405 a, includes the management component. In some embodiments,the management component is referred to as a tools stack. In one ofthese embodiments, the management component is the tools stack 404described above in connection with FIG. 4A. In other embodiments, themanagement component 404 provides a user interface for receiving, from auser such as an administrator, an identification of a virtual machine406 to provision and/or execute. In still other embodiments, themanagement component 404 provides a user interface for receiving, from auser such as an administrator, the request for migration of a virtualmachine 406 b from one physical machine 100 to another. In furtherembodiments, the management component 404 a identifies a computingdevice 100 b on which to execute a requested virtual machine 406 d andinstructs the hypervisor 401 b on the identified computing device 1006to execute the identified virtual machine; such a management componentmay be referred to as a pool management component.

Referring now to FIG. 4C, embodiments of a virtual application deliverycontroller or virtual appliance 450 are depicted. In brief overview, anyof the functionality and/or embodiments of the appliance 200 (e.g., anapplication delivery controller) described above in connection withFIGS. 2A and 2B may be deployed in any embodiment of the virtualizedenvironment described above in connection with FIGS. 4A and 4B. Insteadof the functionality of the application delivery controller beingdeployed in the form of an appliance 200, such functionality may bedeployed in a virtualized environment 400 on any computing device 100,such as a client 102, server 106 or appliance 200.

Referring now to FIG. 4C, a diagram of an embodiment of a virtualappliance 450 operating on a hypervisor 401 of a server 106 is depicted.As with the appliance 200 of FIGS. 2A and 2B, the virtual appliance 450may provide functionality for availability, performance, offload andsecurity. For availability, the virtual appliance may perform loadbalancing between layers 4 and 7 of the network and may also performintelligent service health monitoring. For performance increases vianetwork traffic acceleration, the virtual appliance may perform cachingand compression. To offload processing of any servers, the virtualappliance may perform connection multiplexing and pooling and/or SSLprocessing. For security, the virtual appliance may perform any of theapplication firewall functionality and SSL VPN function of appliance200.

Any of the modules of the appliance 200 as described in connection withFIG. 2A may be packaged, combined, designed or constructed in a form ofthe virtualized appliance delivery controller 450 deployable as one ormore software modules or components executable in a virtualizedenvironment 300 or non-virtualized environment on any server, such as anoff the shelf server. For example, the virtual appliance may be providedin the form of an installation package to install on a computing device.With reference to FIG. 2A, any of the cache manager 232, policy engine236, compression 238, encryption engine 234, packet engine 240, GUI 210,CLI 212, shell services 214 and health monitoring programs 216 may bedesigned and constructed as a software component or module to run on anyoperating system of a computing device and/or of a virtualizedenvironment 300. Instead of using the encryption processor 260,processor 262, memory 264 and network stack 267 of the appliance 200,the virtualized appliance 400 may use any of these resources as providedby the virtualized environment 400 or as otherwise available on theserver 106.

Still referring to FIG. 4C, and in brief overview, any one or morevServers 275A-275N may be in operation or executed in a virtualizedenvironment 400 of any type of computing device 100, such as any server106. Any of the modules or functionality of the appliance 200 describedin connection with FIG. 2B may be designed and constructed to operate ineither a virtualized or non-virtualized environment of a server. Any ofthe vServer 275, SSL VPN 280, Intranet UP 282, Switching 284, DNS 286,acceleration 288, App FW 290 and monitoring agent may be packaged,combined, designed or constructed in a form of application deliverycontroller 450 deployable as one or more software modules or componentsexecutable on a device and/or virtualized environment 400.

In some embodiments, a server may execute multiple virtual machines 406a-406 n in the virtualization environment with each virtual machinerunning the same or different embodiments of the virtual applicationdelivery controller 450. In some embodiments, the server may execute oneor more virtual appliances 450 on one or more virtual machines on a coreof a multi-core processing system. In some embodiments, the server mayexecute one or more virtual appliances 450 on one or more virtualmachines on each processor of a multiple processor device.

E. Systems and Methods for Providing a Multi-Core Architecture

In accordance with Moore's Law, the number of transistors that may beplaced on an integrated circuit may double approximately every twoyears. However, CPU speed increases may reach plateaus, for example CPUspeed has been around 3.5-4 GHz range since 2005. In some cases, CPUmanufacturers may not rely on CPU speed increases to gain additionalperformance. Some CPU manufacturers may add additional cores to theirprocessors to provide additional performance. Products, such as those ofsoftware and networking vendors, that rely on CPUs for performance gainsmay improve their performance by leveraging these multi-core CPUs. Thesoftware designed and constructed for a single CPU may be redesignedand/or rewritten to take advantage of a multi-threaded, parallelarchitecture or otherwise a multi-core architecture.

A multi-core architecture of the appliance 200, referred to as nCore ormulti-core technology, allows the appliance in some embodiments to breakthe single core performance barrier and to leverage the power ofmulti-core CPUs. In the previous architecture described in connectionwith FIG. 2A, a single network or packet engine is run. The multiplecores of the nCore technology and architecture allow multiple packetengines to run concurrently and/or in parallel. With a packet enginerunning on each core, the appliance architecture leverages theprocessing capacity of additional cores. In some embodiments, thisprovides up to a 7× increase in performance and scalability.

Illustrated in FIG. 5A are some embodiments of work, task, load ornetwork traffic distribution across one or more processor coresaccording to a type of parallelism or parallel computing scheme, such asfunctional parallelism, data parallelism or flow-based data parallelism.In brief overview, FIG. 5A illustrates embodiments of a multi-coresystem such as an appliance 200′ with n-cores, a total of cores numbers1 through N. In one embodiment, work, load or network traffic can bedistributed among a first core 505A, a second core 505B, a third core505C, a fourth core 505D, a fifth core 505E, a sixth core 505F, aseventh core 505G, and so on such that distribution is across all or twoor more of the n cores 505N (hereinafter referred to collectively ascores 505.) There may be multiple VIPs 275 each running on a respectivecore of the plurality of cores. There may be multiple packet engines 240each running on a respective core of the plurality of cores. Any of theapproaches used may lead to different, varying or similar work load orperformance level 515 across any of the cores. For a functionalparallelism approach, each core may run a different function of thefunctionalities provided by the packet engine, a VIP 275 or appliance200. In a data parallelism approach, data may be paralleled ordistributed across the cores based on the Network Interface Card (NIC)or VIP 275 receiving the data. In another data parallelism approach,processing may be distributed across the cores by distributing dataflows to each core.

In further detail to FIG. 5A, in some embodiments, load, work or networktraffic can be distributed among cores 505 according to functionalparallelism 500. Functional parallelism may be based on each coreperforming one or more respective functions. In some embodiments, afirst core may perform a first function while a second core performs asecond function. In functional parallelism approach, the functions to beperformed by the multi-core system are divided and distributed to eachcore according to functionality. In some embodiments, functionalparallelism may be referred to as task parallelism and may be achievedwhen each processor or core executes a different process or function onthe same or different data. The core or processor may execute the sameor different code. In some cases, different execution threads or codemay communicate with one another as they work. Communication may takeplace to pass data from one thread to the next as part of a workflow.

In some embodiments, distributing work across the cores 505 according tofunctional parallelism 500, can comprise distributing network trafficaccording to a particular function such as network input/outputmanagement (NW I/O) 510A, secure sockets layer (SSL) encryption anddecryption 510B and transmission control protocol (TCP) functions 510C.This may lead to a work, performance or computing load 515 based on avolume or level of functionality being used. In some embodiments,distributing work across the cores 505 according to data parallelism540, can comprise distributing an amount of work 515 based ondistributing data associated with a particular hardware or softwarecomponent. In some embodiments, distributing work across the cores 505according to flow-based data parallelism 520, can comprise distributingdata based on a context or flow such that the amount of work 515A-N oneach core may be similar, substantially equal or relatively evenlydistributed.

In the case of the functional parallelism approach, each core may beconfigured to run one or more functionalities of the plurality offunctionalities provided by the packet engine or VIP of the appliance.For example, core 1 may perform network I/O processing for the appliance200′ while core 2 performs TCP connection management for the appliance.Likewise, core 3 may perform SSL offloading while core 4 may performlayer 7 or application layer processing and traffic management. Each ofthe cores may perform the same function or different functions. Each ofthe cores may perform more than one function. Any of the cores may runany of the functionality or portions thereof identified and/or describedin conjunction with FIGS. 2A and 2B. In this the approach, the workacross the cores may be divided by function in either a coarse-grainedor fine-grained manner. In some cases, as illustrated in FIG. 5A,division by function may lead to different cores running at differentlevels of performance or load 515.

In the case of the functional parallelism approach, each core may beconfigured to run one or more functionalities of the plurality offunctionalities provided by the packet engine of the appliance. Forexample, core 1 may perform network I/O processing for the appliance200′ while core 2 performs TCP connection management for the appliance.Likewise, core 3 may perform SSL offloading while core 4 may performlayer 7 or application layer processing and traffic management. Each ofthe cores may perform the same function or different functions. Each ofthe cores may perform, more than one function. Any of the cores may runany of the functionality or portions thereof identified and/or describedin conjunction with FIGS. 2A and 2B. In this the approach, the workacross the cores may be divided by function in either a coarse-grainedor fine-grained manner. In some cases, as illustrated in FIG. 5Adivision by function may lead to different cores running at differentlevels of load or performance.

The functionality or tasks may be distributed in any arrangement andscheme. For example, FIG. 5B illustrates a first core, Core 1 505A,processing applications and processes associated with network I/Ofunctionality 510A. Network traffic associated with network I/O, in someembodiments, can be associated with a particular port number. Thus,outgoing and incoming packets having a port destination associated withNW I/O 510A will be directed towards Core 1 505A which is dedicated tohandling all network traffic associated with the NW I/O port. Similarly,Core 2 505B is dedicated to handling functionality associated with SSLprocessing and Core 4 505D may be dedicated handling all TCP levelprocessing and functionality.

While FIG. 5A illustrates functions such as network I/O, SSL and TCP,other functions can be assigned to cores. These other functions caninclude any one or more of the functions or operations described herein.For example, any of the functions described in conjunction with FIGS. 2Aand 2B may be distributed across the cores on a functionality basis. Insome cases, a first VIP 275A may run on a first core while a second VIP275B with a different configuration may run on a second core. In someembodiments, each core 505 can handle a particular functionality suchthat each core 505 can handle the processing associated with thatparticular function. For example, Core 2 505B may handle SSL offloadingwhile Core 4 505D may handle application layer processing and trafficmanagement.

In other embodiments, work, load or network traffic may be distributedamong cores 505 according to any type and form of data parallelism 540.In some embodiments, data parallelism may be achieved in a multi-coresystem by each core performing the same task or functionally ondifferent pieces of distributed data. In some embodiments, a singleexecution thread or code controls operations on all pieces of data. Inother embodiments, different threads or instructions control theoperation, but may execute the same code. In some embodiments, dataparallelism is achieved from the perspective of a packet engine,vServers (VIPs) 275A-C, network interface cards (NIC) 542D-E and/or anyother networking hardware or software included on or associated with anappliance 200. For example, each core may run the same packet engine orVIP code or configuration but operate on different sets of distributeddata. Each networking hardware or software construct can receivedifferent, varying or substantially the same amount of data, and as aresult may have varying, different or relatively the same amount of load515.

In the case of a data parallelism approach, the work may be divided upand distributed based on VIPs, NICs and/or data flows of the VIPs orNICs. In one of these approaches, the work of the multi-core system maybe divided or distributed among the VIPs by having each VIP work on adistributed set of data. For example, each core may be configured to runone or more VIPs. Network traffic may be distributed to the core foreach VIP handling that traffic. In another of these approaches, the workof the appliance may be divided or distributed among the cores based onwhich NIC receives the network traffic. For example, network traffic ofa first NIC may be distributed to a first core while network traffic ofa second NIC may be distributed to a second core. In some cases, a coremay process data from multiple NICs.

While FIG. 5A illustrates a single vServer associated with a single core505, as is the case for VIP1 275A, VIP2 275B and VIP3 275C. In someembodiments, a single vServer can be associated with one or more cores505. In contrast, one or more vServers can be associated with a singlecore 505. Associating a vServer with a core 505 may include that core505 to process all functions associated with that particular vServer. Insome embodiments, each core executes a VIP having the same code andconfiguration. In other embodiments, each core executes a VIP having thesame code but different configuration. In some embodiments, each coreexecutes a VIP having different code and the same or differentconfiguration.

Like vServers, NICs can also be associated with particular cores 505. Inmany embodiments, NICs can be connected to one or more cores 505 suchthat when a NIC receives or transmits data packets, a particular core505 handles the processing involved with receiving and transmitting thedata packets. In one embodiment, a single NIC can be associated with asingle core 505, as is the case with NIC1 542D and NIC2 542E. In otherembodiments, one or more NICs can be associated with a single core 505.In other embodiments, a single NIC can be associated with one or morecores 505. In these embodiments, load could be distributed amongst theone or more cores 505 such that each core 505 processes a substantiallysimilar amount of load. A core 505 associated with a NIC may process allfunctions and/or data associated with that particular NIC.

While distributing work across cores based on data of VIPs or NICs mayhave a level of independency, in some embodiments, this may lead tounbalanced use of cores as illustrated by the varying loads 515 of FIG.5A.

In some embodiments, load, work or network traffic can be distributedamong cores 505 based on any type and form of data flow. In another ofthese approaches, the work may be divided or distributed among coresbased on data flows. For example, network traffic between a client and aserver traversing the appliance may be distributed to and processed byone core of the plurality of cores. In some cases, the core initiallyestablishing the session or connection may be the core for which networktraffic for that session or connection is distributed. In someembodiments, the data flow is based on any unit or portion of networktraffic, such as a transaction, a request/response communication ortraffic originating from an application on a client. In this manner andin some embodiments, data flows between clients and servers traversingthe appliance 200′ may be distributed in a more balanced manner than theother approaches.

In flow-based data parallelism 520, distribution of data is related toany type of flow of data, such as request/response pairings,transactions, sessions, connections or application communications. Forexample, network traffic between a client and a server traversing theappliance may be distributed to and processed by one core of theplurality of cores. In some cases, the core initially establishing thesession or connection may be the core for which network traffic for thatsession or connection is distributed. The distribution of data flow maybe such that each core 505 carries a substantially equal or relativelyevenly distributed amount of load, data or network traffic.

In some embodiments, the data flow is based on any unit or portion ofnetwork traffic, such as a transaction, a request/response communicationor traffic originating from an application on a client. In this mannerand in some embodiments, data flows between clients and serverstraversing the appliance 200′ may be distributed in a more balancedmanner than the other approached. In one embodiment, data flow can bedistributed based on a transaction or a series of transactions. Thistransaction, in some embodiments, can be between a client and a serverand can be characterized by an IP address or other packet identifier.For example, Core 1 505A can be dedicated to transactions between aparticular client and a particular server, therefore the load 515A onCore 1 505A may be comprised of the network traffic associated with thetransactions between the particular client and server. Allocating thenetwork traffic to Core 1 505A can be accomplished by routing all datapackets originating from either the particular client or server to Core1 505A.

While work or load can be distributed to the cores based in part ontransactions, in other embodiments load or work can be allocated on aper packet basis. In these embodiments, the appliance 200 can interceptdata packets and allocate them to a core 505 having the least amount ofload. For example, the appliance 200 could allocate a first incomingdata packet to Core 1 505A because the load 515A on Core 1 is less thanthe load 515B-N on the rest of the cores 505B-N. Once the first datapacket is allocated to Core 1 505A, the amount of load 515A on Core 1505A is increased proportional to the amount of processing resourcesneeded to process the first data packet. When the appliance 200intercepts a second data packet, the appliance 200 will allocate theload to Core 4 505D because Core 4 505D has the second least amount ofload. Allocating data packets to the core with the least amount of loadcan, in some embodiments, ensure that the load 515A-N distributed toeach core 505 remains substantially equal.

In other embodiments, load can be allocated on a per unit basis where asection of network traffic is allocated to a particular core 505. Theabove-mentioned example illustrates load balancing on a per/packetbasis. In other embodiments, load can be allocated based on a number ofpackets such that every 10, 100 or 1000 packets are allocated to thecore 505 having the least amount of load. The number of packetsallocated to a core 505 can be a number determined by an application,user or administrator and can be any number greater than zero. In stillother embodiments, load can be allocated based on a time metric suchthat packets are distributed to a particular core 505 for apredetermined amount of time. In these embodiments, packets can bedistributed to a particular core 505 for five milliseconds or for anyperiod of time determined by a user, program, system, administrator orotherwise. After the predetermined time period elapses, data packets aretransmitted to a different core 505 for the predetermined period oftime.

Flow-based data parallelism methods for distributing work, load ornetwork traffic among the one or more cores 505 can comprise anycombination of the above-mentioned embodiments. These methods can becarried out by any part of the appliance 200, by an application or setof executable instructions executing on one of the cores 505, such asthe packet engine, or by any application, program or agent executing ona computing device in communication with the appliance 200.

The functional and data parallelism computing schemes illustrated inFIG. 5A can be combined in any manner to generate a hybrid parallelismor distributed processing scheme that encompasses function parallelism500, data parallelism 540, flow-based data parallelism 520 or anyportions thereof. In some cases, the multi-core system may use any typeand form of load balancing schemes to distribute load among the one ormore cores 505. The load balancing scheme may be used in any combinationwith any of the functional and data parallelism schemes or combinationsthereof.

Illustrated in FIG. 5B is an embodiment of a multi-core system 545,which may be any type and form of one or more systems, appliances,devices or components. This system 545, in some embodiments, can beincluded within an appliance 200 having one or more processing cores505A-N. The system 545 can further include one or more packet engines(PE) or packet processing engines (PPE) 548A-N communicating with amemory bus 556. The memory bus may be used to communicate with the oneor more processing cores 505A-N. Also included within the system 545 canbe one or more network interface cards (NIC) 552 and a flow distributor550 which can further communicate with the one or more processing cores505A-N. The flow distributor 550 can comprise a Receive Side Scaler(RSS) or Receive Side Scaling (RSS) module 560.

Further referring to FIG. 5B, and in more detail, in one embodiment thepacket engine(s) 548A-N can comprise any portion of the appliance 200described herein, such as any portion of the appliance described inFIGS. 2A and 2B. The packet engine(s) 548A-N can, in some embodiments,comprise any of the following elements: the packet engine 240, a networkstack 267; a cache manager 232; a policy engine 236; a compressionengine 238; an encryption engine 234; a GUI 210; a CLI 212; shellservices 214; monitoring programs 216; and any other software orhardware element able to receive data packets from one of either thememory bus 556 or the one of more cores 505A-N. In some embodiments, thepacket engine(s) 548A-N can comprise one or more vServers 275A-N, or anyportion thereof. In other embodiments, the packet engine(s) 548A-N canprovide any combination of the following functionalities: SSL VPN 280;Intranet UP 282; switching 284; DNS 286; packet acceleration 288; App FW280; monitoring such as the monitoring provided by a monitoring agent197; functionalities associated with functioning as a TCP stack; loadbalancing; SSL offloading and processing; content switching; policyevaluation; caching; compression; encoding; decompression; decoding;application firewall functionalities; XML processing and acceleration;and SSL VPN connectivity.

The packet engine(s) 548A-N can, in some embodiments, be associated witha particular server, user, client or network. When a packet engine 548becomes associated with a particular entity, that packet engine 548 canprocess data packets associated with that entity. For example, should apacket engine 548 be associated with a first user, that packet engine548 will process and operate on packets generated by the first user, orpackets having a destination address associated with the first user.Similarly, the packet engine 548 may choose not to be associated with aparticular entity such that the packet engine 548 can process andotherwise operate on any data packets not generated by that entity ordestined for that entity.

In some instances, the packet engine(s) 548A-N can be configured tocarry out the any of the functional and/or data parallelism schemesillustrated in FIG. 5A. In these instances, the packet engine(s) 548A-Ncan distribute functions or data among the processing cores 505A-N sothat the distribution is according to the parallelism or distributionscheme. In some embodiments, a single packet engine(s) 548A-N carriesout a load balancing scheme, while in other embodiments one or morepacket engine(s) 548A-N carry out a load balancing scheme. Each core505A-N, in one embodiment, can be associated with a particular packetengine 548 such that load balancing can be carried out by the packetengine. Load balancing may in this embodiment, require that each packetengine 548A-N associated with a core 505 communicate with the otherpacket engines associated with cores so that the packet engines 548A-Ncan collectively determine where to distribute load. One embodiment ofthis process can include an arbiter that receives votes from each packetengine for load. The arbiter can distribute load to each packet engine548A-N based in part on the age of the engine's vote and in some cases apriority value associated with the current amount of load on an engine'sassociated core 505.

Any of the packet engines running on the cores may run in user mode,kernel or any combination thereof. In some embodiments, the packetengine operates as an application or program running is user orapplication space. In these embodiments, the packet engine may use anytype and form of interface to access any functionality provided by thekernel. In some embodiments, the packet engine operates in kernel modeor as part of the kernel. In some embodiments, a first portion of thepacket engine operates in user mode while a second portion of the packetengine operates in kernel mode. In some embodiments, a first packetengine on a first core executes in kernel mode while a second packetengine on a second core executes in user mode. In some embodiments, thepacket engine or any portions thereof operates on or in conjunction withthe NIC or any drivers thereof.

In some embodiments the memory bus 556 can be any type and form ofmemory or computer bus. While a single memory bus 556 is depicted inFIG. 5B, the system 545 can comprise any number of memory buses 556. Inone embodiment, each packet engine 548 can be associated with one ormore individual memory buses 556.

The NIC 552 can in some embodiments be any of the network interfacecards or mechanisms described herein. The NIC 552 can have any number ofports. The NIC can be designed and constructed to connect to any typeand form of network 104. While a single NIC 552 is illustrated, thesystem 545 can comprise any number of NICs 552. In some embodiments,each core 505A-N can be associated with one or more single NICs 552.Thus, each core 505 can be associated with a single NIC 552 dedicated toa particular core 505. The cores 505A-N can comprise any of theprocessors described herein. Further, the cores 505A-N can be configuredaccording to any of the core 505 configurations described herein. Stillfurther, the cores 505A-N can have any of the core 505 functionalitiesdescribed herein. While FIG. 5B illustrates seven cores 505A-G, anynumber of cores 505 can be included within the system 545. Inparticular, the system 545 can comprise “N” cores, where “N” is a wholenumber greater than zero.

A core may have or use memory that is allocated or assigned for use tothat core. The memory may be considered private or local memory of thatcore and only accessible by that core. A core may have or use memorythat is shared or assigned to multiple cores. The memory may beconsidered public or shared memory that is accessible by more than onecore. A core may use any combination of private and public memory. Withseparate address spaces for each core, some level of coordination iseliminated from the case of using the same address space. With aseparate address space, a core can perform work on information and datain the core's own address space without worrying about conflicts withother cores. Each packet engine may have a separate memory pool for TCPand/or SSL connections.

Further referring to FIG. 5B, any of the functionality and/orembodiments of the cores 505 described above in connection with FIG. 5Acan be deployed in any embodiment of the virtualized environmentdescribed above in connection with FIGS. 4A and 4B. Instead of thefunctionality of the cores 505 being deployed in the form of a physicalprocessor 505, such functionality may be deployed in a virtualizedenvironment 400 on any computing device 100, such as a client 102,server 106 or appliance 200. In other embodiments, instead of thefunctionality of the cores 505 being deployed in the form of anappliance or a single device, the functionality may be deployed acrossmultiple devices in any arrangement. For example, one device maycomprise two or more cores and another device may comprise two or morecores. For example, a multi-core system may include a cluster ofcomputing devices, a server farm or network of computing devices. Insome embodiments, instead of the functionality of the cores 505 beingdeployed in the form of cores, the functionality may be deployed on aplurality of processors, such as a plurality of single core processors.

In one embodiment, the cores 505 may be any type and form of processor.In some embodiments, a core can function substantially similar to anyprocessor or central processing unit described herein. In someembodiment, the cores 505 may comprise any portion of any processordescribed herein. While FIG. 5A illustrates seven cores, there can existany “N” number of cores within an appliance 200, where “N” is any wholenumber greater than one. In some embodiments, the cores 505 can beinstalled within a common appliance 200, while in other embodiments thecores 505 can be installed within one or more appliance(s) 200communicatively connected to one another. The cores 505 can in someembodiments comprise graphics processing software, while in otherembodiments the cores 505 provide general processing capabilities. Thecores 505 can be installed physically near each other and/or can becommunicatively connected to each other. The cores may be connected byany type and form of bus or subsystem physically and/or communicativelycoupled to the cores for transferring data between to, from and/orbetween the cores.

While each core 505 can comprise software for communicating with othercores, in some embodiments a core manager (not shown) can facilitatecommunication between each core 505. In some embodiments, the kernel mayprovide core management. The cores may interface or communicate witheach other using a variety of interface mechanisms. In some embodiments,core to core messaging may be used to communicate between cores, such asa first core sending a message or data to a second core via a bus orsubsystem connecting the cores. In some embodiments, cores maycommunicate via any type and form of shared memory interface. In oneembodiment, there may be one or more memory locations shared among allthe cores. In some embodiments, each core may have separate memorylocations shared with each other core. For example, a first core mayhave a first shared memory with a second core and a second share memorywith a third core. In some embodiments, cores may communicate via anytype of programming or API, such as function calls via the kernel. Insome embodiments, the operating system may recognize and supportmultiple core devices and provide interfaces and API for inter-corecommunications.

The flow distributor 550 can be any application, program, library,script, task, service, process or any type and form of executableinstructions executing on any type and form of hardware. In someembodiments, the flow distributor 550 may any design and construction ofcircuitry to perform any of the operations and functions describedherein. In some embodiments, the flow distributor distribute, forwards,routes, controls and/ors manage the distribution of data packets amongthe cores 505 and/or packet engine or VIPs running on the cores. Theflow distributor 550, in some embodiments, can be referred to as aninterface master. In one embodiment, the flow distributor 550 comprisesa set of executable instructions executing on a core or processor of theappliance 200. In another embodiment, the flow distributor 550 comprisesa set of executable instructions executing on a computing machine incommunication with the appliance 200. In some embodiments, the flowdistributor 550 comprises a set of executable instructions executing ona NIC, such as firmware. In still other embodiments, the flowdistributor 550 comprises any combination of software and hardware todistribute data packets among cores or processors. In one embodiment,the flow distributor 550 executes on at least one of the cores 505A-N,while in other embodiments a separate flow distributor 550 assigned toeach core 505A-N executes on an associated core 505A-N. The flowdistributor may use any type and form of statistical or probabilisticalgorithms or decision making to balance the flows across the cores. Thehardware of the appliance, such as a NIC, or the kernel may be designedand constructed to support sequential operations across the NICs and/orcores.

In embodiments where the system 545 comprises one or more flowdistributors 550, each flow distributor 550 can be associated with aprocessor 505 or a packet engine 548. The flow distributors 550 cancomprise an interface mechanism that allows each flow distributor 550 tocommunicate with the other flow distributors 550 executing within thesystem 545. In one instance, the one or more flow distributors 550 candetermine how to balance load by communicating with each other. Thisprocess can operate substantially similarly to the process describedabove for submitting votes to an arbiter which then determines whichflow distributor 550 should receive the load. In other embodiments, afirst flow distributor 550′ can identify the load on an associated coreand determine whether to forward a first data packet to the associatedcore based on any of the following criteria: the load on the associatedcore is above a predetermined threshold; the load on the associated coreis below a predetermined threshold; the load on the associated core isless than the load on the other cores; or any other metric that can beused to determine where to forward data packets based in part on theamount of load on a processor.

The flow distributor 550 can distribute network traffic among the cores505 according to a distribution, computing or load balancing scheme suchas those described herein. In one embodiment, the flow distributor candistribute network traffic according to any one of a functionalparallelism distribution scheme 550, a data parallelism loaddistribution scheme 540, a flow-based data parallelism distributionscheme 520, or any combination of these distribution scheme or any loadbalancing scheme for distributing load among multiple processors. Theflow distributor 550 can therefore act as a load distributor by takingin data packets and distributing them across the processors according toan operative load balancing or distribution scheme. In one embodiment,the flow distributor 550 can comprise one or more operations, functionsor logic to determine how to distribute packers, work or loadaccordingly. In still other embodiments, the flow distributor 550 cancomprise one or more sub operations, functions or logic that canidentify a source address and a destination address associated with adata packet, and distribute packets accordingly.

In some embodiments, the flow distributor 550 can comprise areceive-side scaling (RSS) network driver, module 560 or any type andform of executable instructions which distribute data packets among theone or more cores 505. The RSS module 560 can comprise any combinationof hardware and software, In some embodiments, the RSS module 560 worksin conjunction with the flow distributor 550 to distribute data packetsacross the cores 505A-N or among multiple processors in amulti-processor network. The RSS module 560 can execute within the NIC552 in some embodiments, and in other embodiments can execute on any oneof the cores 505.

In some embodiments, the RSS module 560 uses the MICROSOFTreceive-side-scaling (RSS) scheme. In one embodiment, RSS is a MicrosoftScalable Networking initiative technology that enables receiveprocessing to be balanced across multiple processors in the system whilemaintaining in-order delivery of the data. The RSS may use any type andform of hashing scheme to determine a core or processor for processing anetwork packet.

The RSS module 560 can apply any type and form hash function such as theToeplitz hash function. The hash function may be applied to the hashtype or any the sequence of values. The hash function may be a securehash of any security level or is otherwise cryptographically secure. Thehash function may use a hash key. The size of the key is dependent uponthe hash function. For the Toeplitz hash, the size may be 40 bytes forIPv6 and 16 bytes for IPv4.

The hash function may be designed and constructed based on any one ormore criteria or design goals. In some embodiments, a hash function maybe used that provides an even distribution of hash result for differenthash inputs and different hash types, including TCP/IPv4, TCP/IPv6,IPv4, and IPv6 headers. In some embodiments, a hash function may be usedthat provides a hash result that is evenly distributed when a smallnumber of buckets are present (for example, two or four). In someembodiments, hash function may be used that provides a hash result thatis randomly distributed when a large number of buckets were present (forexample, 64 buckets). In some embodiments, the hash function isdetermined based on a level of computational or resource usage. In someembodiments, the hash function is determined based on ease or difficultyof implementing the hash in hardware. In some embodiments, the hashfunction is determined based on the ease or difficulty of a maliciousremote host to send packets that would all hash to the same bucket.

The RSS may generate hashes from any type and form of input, such as asequence of values. This sequence of values can include any portion ofthe network packet, such as any header, field or payload of networkpacket, or portions thereof. In some embodiments, the input to the hashmay be referred to as a hash type and include any tuples of informationassociated with a network packet or data flow, such as any of thefollowing: a four tuple comprising at least two IP addresses and twoports; a four tuple comprising any four sets of values; a six tuple; atwo tuple; and/or any other sequence of numbers or values. The followingare example of hash types that may be used by RSS:

-   -   4-tuple of source TCP Port, source IP version 4 (IPv4) address,        destination TCP Port, and destination IPv4 address.    -   4-tuple of source TCP Port, source IP version 6 (IPv6) address,        destination TCP Port, and destination IPv6 address.    -   2-tuple of source IPv4 address, and destination IPv4 address.    -   2-tuple of source IPv6 address, and destination IPv6 address.    -   2-tuple of source IPv6 address, and destination IPv6 address,        including support for parsing IPv6 extension headers.

The hash result or any portion thereof may used to identify a core orentity, such as a packet engine or VIP, for distributing a networkpacket. In some embodiments, one or more hash bits or mask are appliedto the hash result. The hash bit or mask may be any number of bits orbytes. A NIC may support any number of bits, such as seven bits. Thenetwork stack may set the actual number of bits to be used duringinitialization. The number will be between 1 and 7, inclusive.

The hash result may be used to identify the core or entity via any typeand form of table, such as a bucket table or indirection table. In someembodiments, the number of hash-result bits are used to index into thetable. The range of the hash mask may effectively define the size of theindirection table. Any portion of the hash result or the hash resultitself may be used to index the indirection table. The values in thetable may identify any of the cores or processor, such as by a core orprocessor identifier. In some embodiments, all of the cores of themulti-core system are identified in the table. In other embodiments, aport of the cores of the multi-core system are identified in the table.The indirection table may comprise any number of buckets for example 2to 128 buckets that may be indexed by a hash mask. Each bucket maycomprise a range of index values that identify a core or processor. Insome embodiments, the flow controller and/or RSS module may rebalancethe network rebalance the network load by changing the indirectiontable.

In some embodiments, the multi-core system 575 does not include a RSSdriver or RSS module 560. In some of these embodiments, a softwaresteering module (not shown) or a software embodiment of the RSS modulewithin the system can operate in conjunction with or as part of the flowdistributor 550 to steer packets to cores 505 within the multi-coresystem 575.

The flow distributor 550, in some embodiments, executes within anymodule or program on the appliance 200, on any one of the cores 505 andon any one of the devices or components included within the multi-coresystem 575. In some embodiments, the flow distributor 550′ can executeon the first core 505A, while in other embodiments the flow distributor550″ can execute on the NIC 552. In still other embodiments, an instanceof the flow distributor 550′ can execute on each core 505 included inthe multi-core system 575. In this embodiment, each instance of the flowdistributor 550′ can communicate with other instances of the flowdistributor 550′ to forward packets back and forth across the cores 505.There exist situations where a response to a request packet may not beprocessed by the same core, i.e. the first core processes the requestwhile the second core processes the response. In these situations, theinstances of the flow distributor 550′ can intercept the packet andforward it to the desired or correct core 505, i.e. a flow distributorinstance 550′ can forward the response to the first core. Multipleinstances of the flow distributor 550′ can execute on any number ofcores 505 and any combination of cores 505.

The flow distributor may operate responsive to any one or more rules orpolicies. The rules may identify a core or packet processing engine toreceive a network packet, data or data flow. The rules may identify anytype and form of tuple information related to a network packet, such asa 4-tuple of source and destination IP address and source anddestination ports. Based on a received packet matching the tuplespecified by the rule, the flow distributor may forward the packet to acore or packet engine. In some embodiments, the packet is forwarded to acore via shared memory and/or core to core messaging.

Although FIG. 5B illustrates the flow distributor 550 as executingwithin the multi-core system 575, in some embodiments the flowdistributor 550 can execute on a computing device or appliance remotelylocated from the multi-core system 575. In such an embodiment, the flowdistributor 550 can communicate with the multi-core system 575 to takein data packets and distribute the packets across the one or more cores505. The flow distributor 550 can, in one embodiment, receive datapackets destined for the appliance 200, apply a distribution scheme tothe received data packets and distribute the data packets to the one ormore cores 505 of the multi-core system 575. In one embodiment, the flowdistributor 550 can be included in a router or other appliance such thatthe router can target particular cores 505 by altering meta dataassociated with each packet so that each packet is targeted towards asub-node of the multi-core system 575. In such an embodiment, CISCO'svn-tag mechanism can be used to alter or tag each packet with theappropriate meta data.

Illustrated in FIG. 5C is an embodiment of a multi-core system 575comprising one or more processing cores 505A-N. In brief overview, oneof the cores 505 can be designated as a control core 505A and can beused as a control plane 570 for the other cores 505. The other cores maybe secondary cores which operate in a data plane while the control coreprovides the control plane. The cores 505A-N may share a global cache580. While the control core provides a control plane, the other cores inthe multi-core system form or provide a data plane. These cores performdata processing functionality on network traffic while the controlprovides initialization, configuration and control of the multi-coresystem.

Further referring to FIG. 5C, and in more detail, the cores 505A-N aswell as the control core 505A can be any processor described herein.Furthermore, the cores 505A-N and the control core 505A can be anyprocessor able to function within the system 575 described in FIG. 5C.Still further, the cores 505A-N and the control core 505A can be anycore or group of cores described herein. The control core may be adifferent type of core or processor than the other cores. In someembodiments, the control may operate a different packet engine or have apacket engine configured differently than the packet engines of theother cores.

Any portion of the memory of each of the cores may be allocated to orused for a global cache that is shared by the cores. In brief overview,a predetermined percentage or predetermined amount of each of the memoryof each core may be used for the global cache. For example, 50% of eachmemory of each code may be dedicated or allocated to the shared globalcache. That is, in the illustrated embodiment, 2 GB of each coreexcluding the control plane core or core 1 may be used to form a 28 GBshared global cache. The configuration of the control plane such as viathe configuration services may determine the amount of memory used forthe shared global cache. In some embodiments, each core may provide adifferent amount of memory for use by the global cache. In otherembodiments, any one core may not provide any memory or use the globalcache. In some embodiments, any of the cores may also have a local cachein memory not allocated to the global shared memory. Each of the coresmay store any portion of network traffic to the global shared cache.Each of the cores may check the cache for any content to use in arequest or response. Any of the cores may obtain content from the globalshared cache to use in a data flow, request or response.

The global cache 580 can be any type and form of memory or storageelement, such as any memory or storage element described herein. In someembodiments, the cores 505 may have access to a predetermined amount ofmemory (i.e. 32 GB or any other memory amount commensurate with thesystem 575). The global cache 580 can be allocated from thatpredetermined amount of memory while the rest of the available memorycan be allocated among the cores 505. In other embodiments, each core505 can have a predetermined amount of memory. The global cache 580 cancomprise an amount of the memory allocated to each core 505. This memoryamount can be measured in bytes, or can be measured as a percentage ofthe memory allocated to each core 505. Thus, the global cache 580 cancomprise 1 GB of memory from the memory associated with each core 505,or can comprise 20 percent or one-half of the memory associated witheach core 505. In some embodiments, only a portion of the cores 505provide memory to the global cache 580, while in other embodiments theglobal cache 580 can comprise memory not allocated to the cores 505.

Each core 505 can use the global cache 580 to store network traffic orcache data. In some embodiments, the packet engines of the core use theglobal cache to cache and use data stored by the plurality of packetengines. For example, the cache manager of FIG. 2A and cachefunctionality of FIG. 2B may use the global cache to share data foracceleration. For example, each of the packet engines may storeresponses, such as HTML data, to the global cache. Any of the cachemanagers operating on a core may access the global cache to servercaches responses to client requests.

In some embodiments, the cores 505 can use the global cache 580 to storea port allocation table which can be used to determine data flow basedin part on ports. In other embodiments, the cores 505 can use the globalcache 580 to store an address lookup table or any other table or listthat can be used by the flow distributor to determine where to directincoming and outgoing data packets. The cores 505 can, in someembodiments read from and write to cache 580, while in other embodimentsthe cores 505 can only read from or write to cache 580. The cores mayuse the global cache to perform core to core communications.

The global cache 580 may be sectioned into individual memory sectionswhere each section can be dedicated to a particular core 505. In oneembodiment, the control core 505A can receive a greater amount ofavailable cache, while the other cores 505 can receiving varying amountsor access to the global cache 580.

In some embodiments, the system 575 can comprise a control core 505A.While FIG. 5C illustrates core 1 505A as the control core, the controlcore can be any core within the appliance 200 or multi-core system.Further, while only a single control core is depicted, the system 575can comprise one or more control cores each having a level of controlover the system. In some embodiments, one or more control cores can eachcontrol a particular aspect of the system 575. For example, one core cancontrol deciding which distribution scheme to use, while another corecan determine the size of the global cache 580.

The control plane of the multi-core system may be the designation andconfiguration of a core as the dedicated management core or as a mastercore. This control plane core may provide control, management andcoordination of operation and functionality the plurality of cores inthe multi-core system. This control plane core may provide control,management and coordination of allocation and use of memory of thesystem among the plurality of cores in the multi-core system, includinginitialization and configuration of the same. In some embodiments, thecontrol plane includes the flow distributor for controlling theassignment of data flows to cores and the distribution of networkpackets to cores based on data flows. In some embodiments, the controlplane core runs a packet engine and in other embodiments, the controlplane core is dedicated to management and control of the other cores ofthe system.

The control core 505A can exercise a level of control over the othercores 505 such as determining how much memory should be allocated toeach core 505 or determining which core 505 should be assigned to handlea particular function or hardware/software entity. The control core505A, in some embodiments, can exercise control over those cores 505within the control plan 570. Thus, there can exist processors outside ofthe control plane 570 which are not controlled by the control core 505A.Determining the boundaries of the control plane 570 can includemaintaining, by the control core 505A or agent executing within thesystem 575, a list of those cores 505 controlled by the control core505A. The control core 505A can control any of the following:initialization of a core; determining when a core is unavailable;re-distributing load to other cores 505 when one core fails; determiningwhich distribution scheme to implement; determining which core shouldreceive network traffic; determining how much cache should be allocatedto each core; determining whether to assign a particular function orelement to a particular core; determining whether to permit cores tocommunicate with one another; determining the size of the global cache580; and any other determination of a function, configuration oroperation of the cores within the system 575.

F. Systems and Methods for Efficient Xpath Processing

In various embodiments of data communications and processing systems,XML or XML-like content is processed at intermediate or end devices, forexample to identify and extract particular elements in XML documents. Insome embodiments, the content may also be validated or processed priorto leaving a source device. A document (e.g., of XML content) may belogically represented as a stack of nodes or elements. In someembodiments, Xpath or similar languages provide the language capabilityto define expressions for identifying content elements. Processing ofthe identification further includes matching expressions (e.g., inXpath) to actual elements in the document. As an example of an XML-likecontent, JSON is sometimes an alternative to XML. In some embodiments,JSON content shares similarities to XML content in structure.Accordingly, in various embodiments, Xpath expressions can be adapted toapply to JSON and other similarly-structured documents.

As described below, various embodiments of the systems and methods forXpath processing can be used to reliably identify specific elements inXML or XML-like content. Elements of content described herein are alsosometimes referred to as nodes. These systems and methods may handlesome or all special cases of syntax and/or normal character sets of aplurality of languages (e.g., XML and JSON). These systems and methodsmay be used to find nodes in certain useful contexts. For example and inone embodiment, systems and methods may be used for locating a node thathas a specific parent or has a specific attribute with a particularrange of value. These systems and methods may be used to determinewhether one or more nodes exist in a certain context. These systems andmethods may be used to extract or return content or information of suchnodes. These systems and methods may be used to conditionally (e.g., viaXpath expressions) perform actions based on the XML content.Furthermore, some embodiments of the systems and methods describedherein can be used to alter XML documents structurally. For example andin one embodiment, the Xpath processing can identify content elementsfor rewrite (i.e., determining where, when and what to rewrite, e.g.,replace, delete, insert-before and/or insert-after).

Referring to FIG. 6A, an embodiment of a system 600 for efficientmatching of Xpath expressions to elements in an XML, JSON, or othersimilarly-structured content 699 or document is depicted. In briefoverview, the system includes an Xpath engine 689, a parser 644 and astorage device. As used herein, a document may be any unit of content699 comprising one or more related elements representing a portion ofthe content 699. The parser 644 may receive and process a document, andcan represent the document as a stack of nodes 677. The stack of nodes677 is stored or maintained in the storage device. In some embodiments,the Xpath engine 689 includes an expression evaluator 687 and a nodetracer 688. The Xpath engine 689 may receive an Xpath expression 678.The expression evaluator 687 may parse and identify a plurality of stepsfor the expression. The node tracer 688 may traverse the stack of nodes677 while in communication with the expression evaluator 687 to matchthe steps to nodes in the stack of nodes 677. Based on the matching ofsteps and/or tracing, the Xpath engine 689 may determine if the Xpathexpression 678 is matched.

Although some of the steps described herein may be identified asperformed by the Xpath engine 689 or by some component or module of theXpath engine 689, it should be understood that any other component ormodule of the system may perform the same or substantially the samesteps in various embodiments without departing from the spirit and scopeof the invention. In addition, although generally described with respectto a stack of nodes 677, it should be recognized that the presentsystems and methods may operate on any suitable data structure thatrepresents received content 699. Moreover, although generally describedherein with respect to an Xpath expression 678 or path expression, itshould be recognized that any other suitable types of expression can beused for matching elements in received content 699 in accordance withthe systems and methods disclosed herein. Similarly, XML documents ordocuments are generally referred to for illustration purposes althoughany other type and/or unit of content 699 may be processed using thesystems and methods described in this disclosure.

In further details of FIG. 6A, one or more components of the system 600may reside on any one or more devices having one or more features of anyembodiments of the computing device 100, client 102, server 106 andappliance 200 described above in connection with FIGS. 1A-1H, 2A-2B, 3,4A-4C, 5A-5C. For example and in one embodiment, the Xpath engine 689and the storage device may reside on a network appliance 200, while theparser 644 may reside in a peripheral device of the network appliance200. In some embodiments, the components depicted in FIG. 6A may beconstructed and packaged as a standalone product. One or more componentsof the system may operate sequentially, in parallel and/orindependently. For example and in some embodiments, the parser 644 mayprocess an XML document at any time before the Xpath engine 689 is readyto analyze the stack of nodes 677 (hereafter sometimes referred to as“node stack”, “node tree”, or “stack”). In one embodiment, the XMLdocument and the Xpath expression 678 may be processed independently atany point in time prior to any matching operation.

The parser 644 may be designed and constructed to receive and processany type and form of content 699. The content 699 may be any version,variation and/or extension of XML or XML-like language, such as HTML,JSON, troff, XSLT, LaTex and other markup and/or document-structuringlanguage. The content 699 may be any version, variation and/or extensionof computer, scripting, programming, object-oriented, hardware designand/or compiler language, such as perl, python, C, C++, Pascal, Fortran,Javascript, Verilog, VHDL and SQL. In some embodiments, the parser 644may process one or more natural languages and represent elementsexpressed or inherent in these languages into a node stack 677. Theparser 644 may process content 699, data, material, programs, scriptsand/or expressions (hereafter sometimes generally referred to as“content”) from any one or more of these languages into elements whichmay be related logically and/or hierarchically either in structure,meaning, semantics and/or other characteristics.

The parser 644 may comprise hardware or any combination of software andhardware. The parser 644 may include an application, program, library,script, process, task, thread or any type and form of executableinstructions that executes on one or more processors or cores of adevice. In some embodiments, the parser 644 is a universal ormulti-language parser 644. In other embodiments, the parser 644 may bedesigned and constructed to process or analyze any one or more specificlanguages. The parser 644 may be constructed, configured and/or adaptedto process, decompose, extract, parse or synthesize any portion ofcontent 699 into elements or nodes (hereafter sometimes referred tointerchangeably as “elements” or “nodes”). The parser 644 may relate,organize and/or represent these nodes as a stack of nodes 677 or anyother data structure or representation.

The parser 644 may operate, or be configured to operate at any level ofabstraction or granularity of information. For example and in oneembodiment, the parser 644 may be configured to retain all orsubstantially all information embodied in a portion of content 699. Inone embodiment, the parser 644 may be designed and/or configured toextract, infer or process elements selectively, e.g., to minimize memoryand/or storage footprint, and/or meet system performance requirements.The parser 644 may designed and/or configured to extract, infer orprocess elements at a level sufficient to meet application needs. Insome embodiments, the parser 644 is designed and constructed torepresent content 699 efficiently in a data structure, e.g., a stack ofnodes 677. The parser 644 may be designed and constructed to representcontent 699 in a data structure that is easy to access, store, analyzeand/or process.

The stack of nodes 677 may be implemented in any type or form orcombination of data structure, data representation and/or dataassociation. The stack of nodes 677 may be structurally ordered orarranged via any association or relation. For example and in oneembodiment, the stack of nodes 677 may be represented logically orstructurally as a network, tree, flow-chart or state-machine. Each nodemay represent any type or form of element which may be assigned any oneor more of an identifier, name, level in a hierarchy, attribute,property, characteristic and/or data, any of which may be used inrelation to other nodes. The stack of nodes 677 may be stored in anytype, form or combination of data structures in memory, including butnot limited to tables, lists, hashes, forms, name-field pairs, links,pointers, indexes and/or dictionaries.

In some embodiments, each node includes, stores and/or is linked toinformation including one or more of: a type of the node, a name of thenode, and a namespace of the node. In one embodiment, node names areimplemented or stored in one or more hashes or other suitable datastructure, e.g., in the storage device. Node types (e.g., unnamed and/ornamed node types) may be indexed in a table or other suitable datastructure, e.g., in the storage device. Each node may be linked, via anyhash key, index or entry of any of these data structures, tonode-specific information (e.g., a type of the node, a name of the node,and a namespace of the node). In various embodiments, the stack of nodes677 may be static or can dynamically change in time and/or responsive tocertain events, e.g., a transmission of an updated XML document or aJavascript executing in a HTML page.

In some embodiments, the parser 644 may parse and/or extract certaininformation that is transmitted to another module that filters and/ororganize the information and/or populate a data structure representingthe stack of nodes 677. In other embodiments, the parser 644 organizesthe information into and/or populates the data structure representingthe stack of nodes 677. The parser 644 may store or maintain the stackof nodes 677 in any type or form of memory and/or storage device(hereafter generally referred to as “storage device”), incorporating oneor more features from any embodiment of memory 140 and/or storagedevices 122, 128, 264, 428 described above in connection with FIGS. 1E,2A and 4A. For example and in one embodiment, the storage device maycomprise or be part of a storage area network (SAN).

In association with or independent of the document 699 received andprocessed by the parser 644, the Xpath engine 689 may receive an Xpathexpression 678. An Xpath expression 678 may be any type or form ofcollection or string of characters. The Xpath engine 689 may support anytype or form, or subset of characters, such as unicode characters. Insome embodiments, the Xpath engine 689 may support any type or form ofcharacters supported by the languages (e.g., XML and JSON) that theparser 644 and/or node stack 677 supports. In certain embodiments, thesupported types or forms of characters may be defined by any one or moreof: W3C recommendation for Xpath, XML specification and extensions, andthe requirements of the system 600. For example and in one embodiment,the system 600 may need to support a subset of Xpath location pathexpressions. Accordingly, the system 600 may need to support characters,constructs and/or features included in this subset. For example and inone embodiment, the system 600 may support a subset including but notlimited to: 1) some or all axes (e.g., that do not require backwardtraversal), 2) some or all node tests, 3) some or all multi-steplocation paths, 4) some or all predicates, 5) some or all abbreviatedand non-abbreviated syntax, and 6) some or all protocol interchange (PI)and/or protocol interchange using XML languages (PIXL) functions.

In some embodiments, the supported subset is selected or defined to meetoperational requirements or recommendations, which may include:efficient Xpath processing, fast Xpath processing, low memory footprint,streaming of XML content 699, no or minimal backtracking of XML content699 during processing, and parallel processing of portions of XMLcontent 699. Support for a streaming or substantially streamingimplementation may help avoid memory and/or storage size limitations. Insome embodiments, the system is designed and constructed so thatstandard languages (e.g., Xpath) is supported with little or nomodification. In certain embodiments, the system supports or requiressome subset of Xpath processing, such as identification or location ofXML elements and/or evaluation of expressions into certain types (e.g.,Boolean) of results. By way of illustration and not to be construed aslimiting in any way, some embodiments of system 600 may support thefollowing:

-   -   axes that do not require backward traversal, for example: child,        attribute, descendant, descendant-or-self, namespace, and self.        Some axes may not be implemented because of limitations and/or        difficulty in processing streaming XML content 699. Examples of        axes that may be supported:

/a/b/c /a/@b /a/attribute::b /a//b /a/descendant::b /a/./b

-   -   Certain node tests, which may include testing for all node types        and tests for names (e.g., wild-carded tests). Examples of node        tests that may be supported:

//a //a/*/b //@ns:a //ns:* //@a //a/text( )

-   -   Some or all valid combinations of the supported axes and node        tests may be supported with multi-step location paths.    -   Certain predicates (“filters”), such as predicates that check        for attributes on elements (e.g., either check that an attribute        exists or that an attribute has a specific string value).        Examples of predicates that may be supported:

//a/b[@c] //a/b[@c=‘d’] //a/b[@c=‘d’][@e=‘f’] //a/b[@*=‘d’]//a[@b][@c=‘d’]/e //a/b[@c=concat(“He said “, “‘I can', ’“t do it.”,””)]

-   -   -   In some embodiments, certain combinations of predicates in            an expression may be supported. In certain embodiments,            element names may not contain wildcards. In one embodiment,            a predicate that uses a literal index into the set of            matches for an expression (i.e., providing the Nth match,            not the default first one) may be supported, e.g.,            (/a/b/c)[5].        -   The results from the supported expressions may be converted            to numbers or tested for existence. Some of the results can            also be converted to strings, e.g., conversion of node sets            to strings. Examples may include:

Boolean(/a/b/c) number(/a/b/@c) string(/a/b/c) or just /a/b/c

-   -   Some abbreviated and/or non-abbreviated syntax may be supported,        e.g.,

Either //a[@b] or//a[attribute::b] Either //a[2] or //a[position( )=2]Either /a//b or /a/descendant-or-self::node( )/b

-   -   Some PI or PIXL functions in connection with Xpath may be        supported, e.g.,        -   xpath(xp % xpath-expr %)—can evaluate the given xpath            expression by parsing the XML text, where “%” can be            replaced by any character that is not in xpath-expr (use of            “%” may be recommended) and xpath-expr is the Xpath            expression 678; the result can be a string, Boolean, or            number (double). For example and in one embodiment, if the            document is            -   <a><b><c><d>foo</d><d>bar</d></c><c><d>baz</d></c></b></a>            -   then the result of “xpath(xp %//c/d %)” is the string                “foobar”.        -   xpath_json(xp % xpath-expr %)—in some embodiments, this            function is similar to, or the same as the xpath( )            function, a difference being that the document is parsed            using a JSON parser.        -   xpath_with_markup(xp % xpath-expr %)—this can return a            string that may include the surrounding and enclosed markup            for the node selected, such as the begin and end tags for            elements. For example and in one embodiment, if the document            is            -   <a><b><c><d>foo</d><d>bar</d></c><c><d>baz</d></c></b></a>            -   then the result of “xpath_with_markup(xp %//c/d %)” is                the string            -   <c><d>foo</d><d>bar</d></c>        -   xpath_json_with_markup(xp % xpath-expr %)—in some            embodiments, this is similar to, or the same as the            xpath_with_markup( ) function, one exception being that the            document is parsed using a JSON parser.

In some embodiments, the Xpath engine 689 is designed, constructed,and/or configured to meet certain operational requirements orrecommendations, such as those discussed above (e.g., fast Xpathmatching and/or support streaming content 699). The Xpath engine 689 mayinclude any type or form of hardware and/or combination of hardware andsoftware. The Xpath engine 689 may include any application, program,library, script, process, task, thread or any type and form ofexecutable instructions that executes on any processor or core of adevice. The Xpath engine 689 may include one or more modules includingan expression evaluator 687 and a node tracer 688. Any one or more ofthese modules may have or inherit some attributes of the Xpath engine689. Any one or more of these modules may comprise some portion of Xpathengine 689, e.g., the hardware or combination of hardware and/orsoftware. The Xpath engine 689 may receive one or more messages and/orcommands from any one or more: users, programs, processing modules anddevices. The Xpath engine 689, via the expression evaluator 687, mayidentify, extract or infer one or more Xpath expressions from the one ormore messages and/or commands.

The expression evaluator 687 may be designed, constructed and/orconfigured to identify, extract, infer and/or process any Xpath orXpath-like expressions. Xpath-like expressions may, for example, includesome embodiments of regular expressions (e.g., regexp used in Perl) formatching text-strings. In some embodiments, the expression is a pathexpression. A path expression may be any type or form of expression fordefining, locating and/or identifying a range, type and/or value ofcontent element(s). The expression evaluator 687 may process an (e.g.,Xpath) expression, including one or more of, but not limited to thefollowing steps: 1) validate that the expression is well-formed (notdefective), 2) validate that the expression has portions or elementsthat are supported by the system, 3) remove, filter, modify or transformthe elements or portions that are not well-formed and/or supported, 4)notify the sender of the expression if any element or portion of theexpression is not well-formed and/or supported (e.g., to resend a newexpression), 5) determine if the expression is a multi-step expression,6) partition the expression into one or more steps, 7) assign anidentifier to each step, 8) match each step to one or more nodes thatthe node tracer 688 identifies to the expression evaluator 687, 9)identify each node that matches to the node tracer 688, 10) determine tothe node tracer 688 the number of remaining steps (e.g., minimum ormaximum) in the expression for matching at any given node in the stack,and 11) determine whether the Xpath expression 678 matches anycollection of one or more nodes or fails to match.

The expression evaluator 687 may identify any portion or element of theexpression, e.g., step, axes, context, node tests and/or predicates.Although these units or constructs may be more familiar in reference toXpath, similar units or constructs in other Xpath-like languages aresimilarly supported. The expression evaluator 687 may apply any functionor translation in connection with any portion of the expression, e.g.,Boolean/string/number function, and PIXL functions. In some embodiments,the expression evaluator 687 may share one or more features of theparser 644. For example, the expression evaluator 687 may validate thata character and/or construct in the expression is supported and/or canbe filtered. The expression evaluator 687 may set, generate and/orassign any type or form of identifier to each step of the expression.The identifier may include any alphanumeric and/or special characters.In some embodiments, the identifier is a binary, hexadecimal or othertype of number. The identifier may indicate the position of the steprelative to other steps in the expression. The identifier may indicate atype of the step, e.g., identifying certain elements (e.g., descendantaxes) in the expression of that step.

The expression evaluator 687 may identify the first step of theexpression starting from the left-end of the expression. In someembodiments, the expression evaluator 687 may identify the first stepstarting from the right-end of the expression. The last step may beidentified as a leaf or leaf step. For each step, the expressionevaluator 687 may attempt to match one or more nodes (e.g., of the samehierarchical level and/or type) identified by the node tracer 688. Theexpression evaluator 687 may process the one or more nodes sequentially,in parallel (e.g., via a plurality of cores operating in parallel), orboth. The expression evaluator 687, operating with the node tracer 688traversing the stack of nodes 677, may process the expression top down,i.e., starting from the top or parent node of the node stack 677 againstthe first step of the expression. For example and in one embodiment, theXpath engine 689 may receive a directive including an Xpath expression678 to identify or locate an element (e.g., address of a user) in an XMLdocument. By way of illustration and in reference to the embodiment of anode stack 677 depicted in FIG. 6A, the expression evaluator 687 mayattempt to match the expression of the first step to the parent node(represented by “Listing”). If this matches, the node tracer 688 assignsand/or sets a flag to the matched node and traverses down the stack tothe next nodes (i.e., “member” and “guest”).

The expression evaluator 687 may check each step against one or moreattributes of a node, including: a type of the node, a name of the node,and namespace of the node. The expression evaluator 687 may use hashing(e.g. of node name) and/or indexing (e.g., of unnamed node types) tomatch the name and/or type of the node. The use of a combination ofhashes and/or indexing may enable quicker and/or more efficientmatching, e.g., in comparison to finer-grained separation of hashes foreach type of information. For example and in one embodiment, the datastructure of the node stack 677 may separate name hashes by node type,separate namespace-qualified nodes from those, that are notnamespace-qualified, and separate namespace-qualified wildcards fromregular wildcards. In this embodiment, for a node that is matched basedon the hash/index combination, the expression evaluator 687 effectivelymatched the node in type, name as well as namespace.

Referring again to the node stack 677 in FIG. 6A, if the first stepmatches (i.e., the “Listing” node), the node tracer 688 traverses downto the next level of nodes (“member” and “guest”) and identifies thesenodes to the expression evaluator 687 to compare against the next stepof the expression. One or both nodes may match the expression of thesecond step. In one embodiment, at most one node will match the step. Insome embodiments, two or more nodes may match a step, e.g., when adescendent axis or a following axes (hereafter sometimes referred to as“descendant axes”) is encountered. Accordingly, the node tracer 688 maystore a flag in the node(s) that matched and traverse to the next nodes.At each step, the corresponding expression may be matched to one or moreof the node's type, name, namespace, etc. A node type may represent anygrouping or category of features or attributes. For example, and in oneembodiment, a node type may indicate that the node or element is a rootnode (e.g., parent node of the whole node stack 677), intermediate(e.g., is a parent to at least one node and a child of at least onenode), or a leaf node (e.g., has at least one parent but no children).Node types may be similar to, or include any one or more of thefollowing types as described by the W3C recommendations: all, attribute,comment, element namespace, processing-instruction, rootsignificant-whitespace, text and whitespace.

At each step, the corresponding expression may include one or morepredicates. A predicate may be described as a filter for a node setidentified by an axes. A predicate may itself be an expression forfiltering nodes based on one or more attributes of a node. A predicatemay filter a node set and create a new node set (e.g. subset of theoriginal node set). A predicate may be used to determine if one or moreconditions are satisfied. The matching and traversal may continue untilone of several events occur. In one embodiment, no nodes matches a stepof the expression. In some embodiments, if one step of the expression donot match any nodes of an XML document, the Xpath expression 678 failsto match. The expression evaluator 687 may determine that the Xpathexpression 678 do not match any elements in the document or portion ofcontent 699.

In some embodiments, the node tracer 688 may find that there are nonodes to match against a step of the expression. In one of theseembodiments, the node tracer 688 may have already encountered one ormore leaf nodes in connection with a previous step of the expression.There may be no child nodes (e.g., of leaf nodes) to match against thecurrent step. In response, the expression evaluator 687 may determinethat the Xpath expression 678 do not match any elements in the documentor portion of content 699. In some embodiments, the Xpath expression 678may determine that there are available nodes, or available (e.g.,minimum) number of levels of nodes in the stack, to check against thenumber of steps in the expression. This determination may occur in apre-check before matching the first step of the expression. In someembodiments, the determination may occur in parallel (e.g., viamulti-core parallel processing) with one or more matching steps, e.g.,so as not to delay the matching operations and/or degrade theperformance of the Xpath engine 689.

In some embodiments, the expression evaluator 687 matches the leaf stepof the expression with a node that is not a leaf node. In otherembodiments, the node tracer 688 reaches a leaf node of the node stack677 that matches the last step of the expression. In some of theseembodiments, the node matches the step if the corresponding node type(e.g., leaf or not a leaf) matches the step. In other embodiments, thenode does not match if the node type required for the last step is aleaf node and the node type of the node checked against the last step isnot a leaf node. In embodiments where a node matches the last step, wemay generally refer to the node as a leaf node.

The node tracer 688 may store a flag in one or more leaf nodes inresponse to matching the last step of the expression. In someembodiments, the node tracer 688 does not store a flag in these leafnodes, e.g., to minimize processing and/or memory footprint. One or moresuch leaf nodes may be matched, corresponding to one or more documentelements that the expression serves to identify. In some embodiments,the expression evaluator 687 may determine that the expression matchedupon matching at least one leaf node. In some embodiments, the Xpathengine 689 provides an indication (e.g., to the user or another device)that the expression matched (i.e., some elements of the document) atthis point. Upon encountering a leaf node, the expression evaluator 687may not be able identify the elements that matched the path expression.Upon encountering a leaf node, the expression evaluator 687 may be ableto identify a count of elements that matched (e.g. corresponding to thenumber of leaf nodes that matched). In certain embodiments of content699 from certain languages and/or using certain expressions, theexpression evaluator 687 may be able identify elements of content 699that matched the path expression. In some embodiments, the Xpath engine689 may store and process node information that matched to determineelements of content 699 that matched the path expression uponencountering a leaf node.

In accordance with one or more embodiments described above and elsewherein this disclosure, the node tracer 688 may be designed, constructedand/or configured to traverse any type or form of data structure of thestack of node. The node tracer 688 may traverse from node to node byaccessing or retrieving one or more portions of the data structure vialinks, pointer or other means. The node tracer 688 may identify any oneor more nodes to the expression evaluator 687 to perform matchingoperations. In some embodiments, the node tracer 688 accesses andtransmits information (e.g., node type, name and namespace) about one ormore nodes to the expression evaluator 687 to perform matchingoperations. In certain embodiments, the node tracer 688 incorporates oneor more features and/or functionalities of the expression evaluator 687.In some embodiments, the node tracer 688 is an agent of the expressionevaluator 687, e.g., traversing the node stack 677 on behalf of theexpression evaluator 687. In one embodiment, a single module of theXpath engine 689 provides some or all functionalities of the node tracer688 and the expression evaluator 687.

As discussed, the node tracer 688 may store a flag with a node thatmatched a step of the expression. In some embodiments, the node tracer688 may add, set, unset, modify a flag to the node. The flag may be anytype or form of indicator, e.g., Boolean (e.g., 1/0, or True/False),text (e.g., “matched” or “not matched”) or otherwise. The flag may serveto indicate that the corresponding node matched a step. The flag mayinclude additional information such as an identifier of thecorresponding matching step. In some embodiments, the data structure ofthe flag is kept simple. In some embodiments, the memory footprint ofthe flag is minimized (e.g., by using a Boolean flag without storingadditional information).

In some embodiments, the node tracer 688 may proceed to traverse thenode stack 677 bottom to top from a leaf node responsive to matching aleaf node. The node tracer 688 may trace along nodes that are flagged,pairing each node with a step (e.g., via the identifier of each step) ofthe expression. In some embodiments, this is akin to stringing beads(i.e., nodes) that were flagged earlier. If for any step, at least oneflagged node is not found, the expression evaluator 687 or the nodetracer 688 may determine that the matching of the expression failed. Ifthe bottom to top tracing reaches the first step of the expression witha flagged node, the expression evaluator 687 may determine that theexpression matched. One or more of the nodes (i.e., stringed beads)traced bottom to top may identify an element of the content 699 thatmatched or satisfied the expression.

If any descendent (or similar) axes (e.g., “//”) is encountered at anystep (e.g., during matching), for example in the middle of theexpression, the node tracer 688 may loop from the corresponding node.This may sometimes be referred to as a loop trace, looping or tracing aloop. In some embodiments, each loop trace may be performed a node at atime against steps of the expression. The loop trace may includeflagging matched nodes while traversing top to bottom and/or tracingflagged nodes while traversing bottom to top. Operations during the looptrace may the same as or substantially the same as the usual top tobottom traversal and/or bottom to top tracing. In some embodiments, ifmultiple descendant axes are encountered, the node tracer 688 may nothave to nest multiple loops corresponding to the multiple descendentaxes. In some of these embodiments, the node tracer 688 may trace theloops sequentially. This may be possible due to one or more restrictionson the syntax or features supported by the expression evaluator 687,such as some of the Xpath features described above. The subset of Xpathexpression 678 syntax or features supported may simplify handling ofloop trace, e.g., including tracing loops sequentially. In some of theseembodiments, because the loops are non-overlapping or non-nested, theXpath engine 689 does not have to process a polynomial combination fromthe corresponding descendent axes. Instead, the Xpath engine 689 mayprocess a linear combination, e.g., bounded by the depth of the nodestack 677.

The expression evaluator 687 and/or parser 644 may be provided by, orinclude any one or more features of any embodiment of the packet engines240, 548 described above in connection with FIGS. 2A and 5B. In someembodiments, the Xpath engine 689 and/or parser 644 may communicativelyinteroperate with the packet engine. For example and in one embodiment,the packet engine may receive a message comprising a command to identifyan element of an XML document. The packet engine may direct the messageor command to the expression evaluator 687 of the Xpath engine 689 forprocessing. The packet engine may receive a message comprising XMLcontent 699. The packet engine may direct the message or content 699 tothe parser 644 for processing.

In some embodiments, such as in a multi-core and/ormulti-virtual-machine system as described above in connection with FIGS.1G-1H, 4A-C and 5A-5C, a plurality of portions of content 699 and/or aplurality of Xpath expressions 678 may be processed in parallel orsubstantially in parallel. For example and in one embodiment, one ormore cores may each execute or support an Xpath engine 689 forprocessing different stacks of nodes, and/or different branches (e.g.,loop traces) of a stack of nodes 677. In another embodiment, one or morecores may each execute or support a parser 644 for processing differentXML documents and/or different portions of a single XML document.

In some embodiments, the systems and methods described herein improvesperformance in matching Xpath expression 678 in one or more ways asfollows: 1) the processing does not require a large memory footprint orstorage space to store information on the node stack 677 (e.g., simpleflag to reflect matching; at most three attributes are stored or linkedfor each node, e.g., node type, name and namespace; no storage ofbacktracking traces because of single-step matching), 2) nobacktracking, which allows streaming of content 699 (e.g., content 699is parsed and processed in a single pass without extensive looping andbacktracking due to multi-step matching and/or descendent axes), 3)avoids exponential blow-up in processing and/or memory requirements(e.g., as described in 1 and 2), and 4) faster processing (e.g., due tosimple one-pass algorithm; support for parallel processing; lessinformation stored and/or processed).

In some embodiments, performance in the systems and methods describedherein may be improved and/or tweaked by applying or leveraging on oneor more of the following. In some embodiments, Boolean results can bethe fastest to evaluate. Therefore, the use of Boolean functions, suchas Boolean(xpath-expression), may improve performance. In someembodiments, it is faster to match an element as the leaf on anexpression than as text( ). One example is “//a” compared to “//a/text()”. However, performance between these may be equivalent if the elementonly has a single text descendant. In some embodiments, the morespecific the node test, generally the faster the system may be inmatching an expression. By supporting, arranging and/or transformingcertain node tests, performance may be enhanced. For example and in oneembodiments, the forms of node tests in decreasing order of performanceare:

“a” or “ns:a” or “processing-instruction(‘a’)” “ns:*” “*” or “text( )”or “processing-instruction( )” or “comment( )” or “/” “node( )” (may beslightly less efficient than “*”, etc.)

Referring now to FIG. 6B, a flow diagram depicting an embodiment ofsteps of a method 650 for efficient Xpath matching of a documentcomprising XML or JSON is shown. In brief overview, at step 601, aparser 644 processes a document comprising XML or JSON and representsthe document as a stack of nodes 677. At step 603, an expressionevaluator 687 of an Xpath engine 689 identifies an Xpath expression 678for processing values in the document. At step 605, a node tracer 688 ofthe Xpath engine 689 traverses the stack of nodes 677 from top to bottomto match each step of a path expression of the Xpath expression 678 to atype and name of one or more nodes in the stack of nodes 677. At step607, the node tracer 688 stores a flag in each node in the stack ofnodes 677 that matches a step of the path expression. At step 609, thenode tracer 688 performs a loop trace for one or more descendant axes inthe path expression, wherein the loop trace comprises tracing one ormore nodes matching the descendant axes. At step 611, the expressionevaluator 687 determines that the path expression is not matched if anysingle step of the path expression fails to match any nodes. At step613, responsive to encountering a leaf node, the node tracer 688 tracesbottom to top from the leaf node to one or more flagged nodes in thestack of nodes 677, and comparing each of the one or more flagged nodesagainst a corresponding step of the path expression. At step 615, theexpression evaluator 687 determines if the path expression is matchedresponsive to the tracing of the flagged nodes.

In further details of step 601, a parser 644 processes an XML orXML-like (e.g., JSON) document and represents the document as a stack ofnodes 677. The parser 644 may receive and/or process any XML or XML-likecontent 699 in one or more messages or documents. The parser 644 mayreceive the content 699 in a streaming or substantially streamingfashion. The parser 644 may identify the language (e.g., XML or anyother language) of the content 699. In some embodiments, the parser 644may identify the version of the language of the content 699. In oneembodiment, the parser 644 may receive an indication of the languageand/or version of the language. For example and in one embodiment, auser configures the parser 644 to process content 699 for a specificlanguage. The parser 644 may process the content 699 in real-time orsubstantially in real-time. The parser 644 may process the content 699one portion at a time, e.g., partition content 699 into documents,sections or segments for separate processing. In some embodiments, theparser 644 may process a plurality of portions of the content 699 inparallel and/or sequentially (e.g., via multi-core processing). Theparser 644 may include or operate with a cache for storing the receivedcontent 699, e.g., while processing a portion of the received content699.

The parser 644 may parse, analyze, extract, decompose, synthesize, inferand/or process the content 699 into elements or nodes which may berelated logically and/or hierarchically either in structure, meaning,semantics and/or other characteristics. The parser 644 may relate,organize and/or represent these nodes into a stack of nodes 677 and/orany data structure. The parser 644 may determine the data structure(e.g., as a node stack 677 and/or amount of information) forrepresenting the content 699 based on a history of similar contentreceived (e.g., statistical information of the similar content and/orperformance of various matching methods or combination of matchingmethods to similar content). In some embodiments, the parser 644processes and/or stores all or substantially all information included ina portion of content 699. In other embodiments, the parser 644 mayextract, infer, store and/or process elements selectively, e.g., tominimize memory and/or storage footprint.

The parser 644 may extract, infer or process elements at a levelsufficient to meet specific application needs and/or performance levels.In some embodiments, a user or a device (e.g., Xpath engine 689) mayindicate to the parser 644 the granularity of information needed for thestack of node or data structure. For example and in one embodiment, theXpath engine 689 may indicate that a level of information suitable for ahybrid matching method or mode may be processed and/or storedaccordingly. In some embodiments, the parser 644 may transform, filteror ignore unsupported and/or defective language constructs in thecontent 699. In certain embodiments, the parser 644 requests the senderof the defective and/or unsupported content 699 to resend or correct thecontent 699.

In some embodiments, the parser 644 represents and/or stores the content699 efficiently in a data structure, for example as a stack of nodes677. The parser 644 may structurally order or arrange the nodes via anyassociation or relation between the nodes. The parser 644 may assignand/or store in each node any one or more of an identifier, name,namespace, level in a hierarchy, type, attribute, property,characteristic and/or other data specific to or associated to the node.In some embodiments, the parser 644 associates or stores in each node anode type, name and namespace. The parser 644 may store, record ororganize node names into one or more hashes and/or other suitable datastructure. The parser 644 may index node types in a table and/or othersuitable data structure. In one embodiment, the parser 644 may indexunnamed node types for organizing and/or retrieving node information.The parser 644 may update the stack of nodes 677 dynamically,periodically and/or upon certain predefined events, such as upon receiptof an updated (e.g., XML) document.

In some embodiments, the parser 644 may parse and/or extract certaininformation from the content 699. The parser 644 may transmit thisinformation to another module that filters and/or organize theinformation and/or populate the data structure representing the stack ofnodes 677. In other embodiments, the parser 644 organizes theinformation and/or populates the data structure representing the stackof nodes 677. The parser 644 may store or maintain the stack of nodes677 in one or more memory or storage devices. The parser 644 may storeor maintain information for each node at a different memory location andcreate or define pointers or links between nodes. In some embodiments,the parser 644 defines the data structure of the node stack 677 and thestorage device (e.g., via a storage manager or device driver) implementsthe data structure in the storage device.

In certain embodiments, the parser 644 does not process received content699 until the Xpath engine 689 sends the parser 644 an indication (e.g.,that Xpath matching is enabled and/or an Xpath expression 678 isvalidated for matching). In some embodiments, the parser 644 sends anindication to the Xpath engine 689 (e.g., that a node stack 677 iscreated) before the Xpath engine 689 performs one or more steps (e.g.,processes an Xpath expression 678 or accesses the node stack 677). Insome embodiments, the parser 644 sends an address, memory location, oridentifier of the node stack 677 to the Xpath engine 689, e.g., foraccessing the node stack 677. In one embodiment, the parser 644 sends anaddress, memory location, or identifier of the node stack's root node tothe Xpath engine 689.

In further details of step 603, an expression evaluator 687 of an Xpathengine 689 identifies an Xpath expression 678 for processing values inthe document. In some embodiments, the Xpath engine 689 receives acommand or message for processing an XML or XML-like document. The Xpathengine 689 may identify that the command or message includes an Xpathexpression 678. The Xpath engine 689 may forward the command or messageto the expression evaluator 687, e.g., responsive to identifying anXpath expression 678 in the command or message. The expression evaluator687 may identify an Xpath expression 678 for identifying an element orlocation in the document. The expression evaluator 687 may identify anXpath expression 678 for identifying or locating one or more elements ofthe content 699 in a context defined by the Xpath expression 678.

The expression evaluator 687 may verify that the Xpath expression 678 iswell-formed (e.g., not defective). The expression evaluator 687 mayvalidate that the expression has elements or features that are supportedby the system. For example and in one embodiment, the expressionevaluator 687 verifies that a character and/or construct in theexpression is supported. The expression evaluator 687 may remove,filter, modify or transform elements or portions that are notwell-formed and/or supported. The expression evaluator 687 may notifythe sender of the Xpath expression 678 (e.g., to correct and/or resendthe expression) if any element or portion of the expression is notwell-formed and/or supported. In some embodiments, the expressionevaluator 687 may validate and/or process the Xpath expression 678 basedon information received from the parser 644, e.g., an identification ofa language and/or version of the language.

The expression evaluator 687 may determine if the expression is amulti-step expression. The expression evaluator 687 may determine orverify that the Xpath expression 678 is a location path expression. Theexpression evaluator 687 may partition the expression into one or moresteps. The expression evaluator 687 may assign a step identifier to eachstep of the path expression. The expression evaluator 687 may identifythe first step of the expression starting from the left-end of theexpression. In some embodiments, the expression evaluator 687 mayidentify the first step starting from the right-end of the expression

In further details of step 605, a node tracer 688 of the Xpath engine689 traverses the stack of nodes 677 from top to bottom to match eachstep of a path expression of the Xpath expression 678 to a type and nameof one or more nodes in the stack of nodes 677. In some embodiments, thenode tracer 688 receives an address, memory location or identifier foraccessing the node stack 677 in the storage device. In otherembodiments, the node tracer 688 polls or checks the storage device fora node tree to analyze. The node tracer 688 may access or retrieve partor all of the stack of nodes 677 from the storage device. The nodetracer 688 may traverse the node stack 677 by accessing elements (e.g.,pointers, links, indexes, tables and/or hashes) in the node stack 677.The node tracer 688 may, in communication with the expression evaluator687, attempt to match nodes of the node stack 677 to each step of theXpath expression 678. The node tracer 688 may identify the root node tothe expression evaluator 687 for matching against the first step of theexpression.

The node tracer 688 may determine whether there are enough nodes in thestack to match the number of steps in the path expression. In oneembodiment, the node tracer 688 determines if there are enough nodes inthe stack to match the minimum number of steps in the path expression.In some embodiments, the node tracer 688 determines if there are enoughnodes in the stack prior to the matching process. For example and in oneembodiment, the Xpath engine 689 may determine that the Xpath expression678 fails to match with the content 699 because there are insufficientnodes in the stack with respect to the Xpath expression 678. The Xpathengine 689 may determine not to proceed with the node stack 677traversal. In other embodiments, the node tracer 688 may determine ifthere are enough nodes in the stack while the matching process proceedsin parallel. In certain embodiments, at any one or more steps of theexpression, the node tracer 688 may determine if there are enough nodesin the stack to match the minimum number of steps remaining in the pathexpression. If there are insufficient nodes in the stack with respect tothe remaining steps in the expression, the Xpath engine 689 maydetermine that the Xpath expression 678 has failed to match.

In some embodiments, the node tracer 688 traverses one or more paths orbranches in the node tree (e.g., corresponding to a descendent axes).The node tracer 688 may identify one or more nodes from the same levelin the node stack 677. The node tracer 688 may identify one or morenodes (from one or more paths or branches) to the expression evaluator687. In other embodiments, each of a plurality of node tracers 688traverses a path, branch or loop trace of the node tree. A node tracer688 (e.g., of the plurality of node tracers) may identify a node to theexpression evaluator 687. The expression evaluator 687 may attempt tomatch an expression of each step with the identified node. Theexpression evaluator 687 may check each step against one or moreattributes of the node, including one or more of: a type of the node, aname of the node, and namespace of the node. The expression evaluator687 may identify any portion or element of the expression of each stepfor evaluation and/or matching, e.g., axes, context, node tests and/orpredicates. The expression evaluator 687 may attempt to match anexpression of each step, including any predicate, with a type and a nameof the identified one or more nodes in the stack of nodes 677.

The expression evaluator 687 may use hashing (e.g. of node name) and/orindexing (e.g., of unnamed node types) to match the name and/or type ofeach node. In one embodiment, the expression evaluator 687 uses hashingto identify one or more nodes with node types that matches theexpression of the step. In some embodiments, the expression evaluator687 may use indexing to match namespace-qualified nodes to theexpression of the step. In certain embodiments, the expression evaluator687 may use indexing to exclude non-namespace-qualified nodes withrespect to the expression of the step. In some embodiments, theexpression evaluator 687 may effectively match a node in type, name aswell as namespace based on a hash/index combination method described insome of the embodiments above. The expression evaluator 687 may applyany function or translation in connection with any portion of theexpression, e.g., Boolean/string/number function, and PIXL functions.The expression evaluator 687 may process the one or more nodessequentially, in parallel (e.g., via multi-core processing), or both.

In further details of step 607, the node tracer 688 stores a flag witheach node in the stack of nodes 677 that matches a step of the pathexpression. The expression evaluator 687 may determine that a step ofthe path expression matches a node identified by the node tracer 688.The expression evaluator 687 may determine that a step of the pathexpression matches a node identified by the node tracer 688 in at leasta type and a name of each of the one or more nodes. In one embodiment,the expression evaluator 687 may determine that a step. of the pathexpression matches one or more nodes identified by the node tracer 688in at least a type, a name and a namespace of each of the one or morenodes.

In response to the matching of the step, the node tracer 688 may store aflag, marker or any other indication with the one or more nodes, e.g.,to indicate the matching of the step to the one or more nodes. Inresponse to the matching of the step, the node tracer 688 may set,unset, update or modify a flag, field or other indicator in the one ormore nodes, e.g., to indicate the matching of the step to the one ormore nodes. In some embodiments, the node tracer 688 stores a Booleanflag in each node in the stack of nodes 677 that matches a step of thepath expression. In other embodiments, the node tracer 688 uses a singlememory bit of the matched node to indicate the matching of the step tothe node. In other embodiments, the node tracer 688 uses one or morebits of memory.

The node tracer 688 may proceed, top to bottom, from each of the one ormore nodes that matched a step of the expression, to the next level ofnodes along one or more paths, branches or loop traces of the node stack677. The node tracer 688 may identify one or more nodes from the nextlevel of nodes to the expression evaluator 687 for matching against anext step of the path expression. In some embodiments, a plurality ofnode tracers 688 may traverse top to bottom to a plurality of paths,branches or loop traces of the node stack 677. Each of the plurality ofnode tracers may identify one or more nodes from the next level of nodesto an expression evaluator 687 (e.g., of a plurality of expressionevaluator 687) for matching against a next step of the path expression.The traversing and/or matching may proceed according to any of theembodiments of steps described above in connection with steps 605 and609.

In further details of step 609, the node tracer 688 performs a looptrace for one or more descendant axes in the path expression. The looptrace may include tracing one or more nodes matching a descendant axes.The expression evaluator 687 may identify a descendent axes in anexpression corresponding to a step of the path expression. Thedescendent axes may trigger a loop trace at that step of the pathexpression. The descendent axes may trigger a loop trace from the one ormore nodes corresponding to that step of the path expression. In someembodiments, the expression evaluator 687 may identify one or moredescendent axes in an expression corresponding to a step of the pathexpression. In certain embodiments, the expression evaluator 687 mayidentify one or more descendent axes in one or more steps of the pathexpression. In these embodiments, the Xpath engine 689 may initiate oneor more loop traces. The Xpath engine 689 may process the one or moreloop traces sequentially, e.g., no nested loops. In some embodiments,the Xpath engine 689 may process a subset of the one or more loop tracessequentially.

Each of the one or more descendent axes may identify one or more pathsor branches for traversing to the next node(s). Each of the one or moredescendent axes may identify one or more nodes for the node tracer 688to traverse to. For each of the one or more nodes, paths or branchesidentified, the Xpath engine 689 may traverse the node stack 677 and/orperform step matching as described herein according to any embodimentsof one or more of steps 605, 607, 611, 613 and 615. For example and inone embodiment, the node tracer 688 may traverse the node stack 677 toone of the one or more nodes identified via a descendent axes in onestep of the path expression. The node tracer 688 may identify this nodeto the expression evaluator 687. The expression evaluator 687 mayattempt to match the next step of the path expression with this node. Ifthe step matches, the Xpath engine 689 may proceed to the next node formatching. The node tracer 688 may traverse the node stack 677 formatching additional steps until the node stack 677 runs out of nodes(see step 611 for corresponding embodiments of steps) or until the nodetracer 688 encounters a leaf node (see step 613 for correspondingembodiments of steps). If the loop trace fails to match, the node tracer688 may exit the loop trace and traverse to another one of the one ormore nodes identified via the descendent axes. The node tracer 688 mayidentify this other node to the expression evaluator 687 and theexpression evaluator 687 may attempt to match the next step of the pathexpression with this other node. This process may repeat until theplurality of loop traces triggered by a descendent axes have beenchecked.

In further details of step 611, the expression evaluator 687 determinesthat the path expression is not matched if any single step of the pathexpression fails to match any nodes. In some embodiments, the expressionevaluator 687 determines that a step expression does not match a nodeidentified by a node tracer 688. The step expression may correspond toany step of the path expression. The expression evaluator 687 maydetermine that the step expression fails to match a node in any one ormore of: a type of the node, a name of the node, and namespace of thenode. In one embodiment, the expression evaluator 687 determines thatthe step expression fails to match a node in a type of the node and aname of the node. In some embodiments, the expression evaluator 687 maydetermine that the path expression is not matched responsive todetermining that the step expression does not match any node.

In some embodiments, the expression evaluator 687 determines that a stepexpression does not match a node identified by a node tracer 688 whilein a loop trace. The step expression may correspond to any step of thepath expression while in the loop trace. The expression evaluator 687may determine that the step expression fails to match a node in any oneor more of: a type of the node, a name of the node, and namespace of thenode. The expression evaluator 687 may determine that the pathexpression is not matched in this loop trace responsive to determiningthat the step expression does not match any node in this loop trace. Theexpression evaluator 687 may proceed to perform matching in another looptrace. For example and in one embodiment, the node tracer 688 may exit aloop trace that does not match and return to the node prior to the startof the loop trace. The node tracer 688 may enter another loop trace bytraversing to an alternate node identified via the same descendent axes.In some embodiments, the expression evaluator 687 determines that thepath expression does not match if each loop trace has at least one stepthat does not match any nodes.

In certain embodiments, the node tracer 688 fails to identify any nodesto any one or more steps of the path expression. In some embodiments,the node tracer 688 may determine that the node stack 677 have run outof nodes along a path in the node stack 677. In some of theseembodiments, the node tracer 688 may determine that the node stack 677have run out of nodes while traversing a loop trace. In response to theabsence of additional nodes to check against one or more remainingsteps, the expression evaluator 687 may determine that the pathexpression failed to match any elements in the content 699.

In further details of step 613, responsive to encountering a leaf node,the node tracer 688 traces bottom to top from the leaf node to one ormore flagged nodes in the stack of nodes 677. In some embodiments, thenode tracer 688 may proceed to traverse the node stack 677 bottom to topfrom a leaf node responsive to matching the leaf node. The node tracer688 may trace along nodes that are flagged. The node tracer 688 may paireach flagged node with a step (e.g., via the identifier of each step) ofthe expression. The node tracer 688 and/or the expression evaluator 687may compare each of the flagged nodes against a corresponding step ofthe path expression. The node tracer 688 may compare each of the one ormore flagged nodes against a step identifier of a corresponding step ofthe path expression. In some embodiments, the node tracer 688 and/or theexpression evaluator 687 may compare each of the flagged nodes against acorresponding step expression. In some embodiments, the bottom to toptracing of flagged nodes is analogous to stringing beads (i.e., nodes)that were flagged earlier.

In further details of step 615, the expression evaluator 687 determinesif the path expression is matched responsive to the tracing of theflagged nodes. In some embodiments, if at least one flagged node is notfound for any step while tracing bottom to top, the expression evaluator687 or the node tracer 688 may determine that the matching of theexpression failed. For example and in one embodiment, where the pathexpression does not use descendent axes, if at least one flagged node isnot found for any step while tracing bottom to top, the expressionevaluator 687 or the node tracer 688 may determine that the matching ofthe expression failed.

In some embodiments, the node tracer 688 traces flagged nodes within aloop trace. In these embodiments, if at least one flagged node is notfound for any step while tracing bottom to top, the expression evaluator687 or the node tracer 688 may determine that the matching of theexpression failed for this trace loop. If at least one flagged node isnot found for any step while tracing bottom to top for every trace looparising from a single descendent axes, the expression evaluator 687 orthe node tracer 688 may determine that the matching failed for the stephaving the descendent axes. In some embodiments, the expressionevaluator 687 or the node tracer 688 may determine that matching of apath expression failed if at least one flagged node is not found for anystep while tracing bottom to top for every trace loop arising from asingle descendent axes.

In some embodiments, the expression evaluator 687 or the node tracer 688may determine that the path expression is not matched if the stack ofnodes 677 runs out of nodes before reaching the first step of the pathexpression while tracing bottom to top. In some embodiments, if thestack of nodes 677 runs out of nodes before reaching the first step ofthe path expression while tracing bottom to top in a trace loop, theexpression evaluator 687 or the node tracer 688 may determine that thepath expression is not matched for this trace loop. If, for each andevery trace loop arising from a single descendent axes, the stack ofnodes 677 runs out of nodes before reaching the first step of the pathexpression while tracing bottom to top in a trace loop, the expressionevaluator 687 or the node tracer 688 may determine that the pathexpression is not matched for the path expression.

In some embodiments, the expression evaluator 687 or the node tracer 688may determine that the path expression is matched if a node of the stackof nodes 677 corresponding to the first step of the path expression isflagged. If the bottom to top tracing reaches the first step of theexpression at the root node, the expression evaluator 687 may determinethat the path expression matched. In some embodiments, if the bottom totop tracing reaches the first step of the expression corresponding to aflagged node, the expression evaluator 687 may determine that the pathexpression matched.

In some embodiments, one or more of the flagged nodes traced bottom totop may be used to identify an element of the content 699 that matchedor satisfied the path expression. One or more of these flagged nodes,ordered from top to bottom, may be used to identify the element of thecontent 699 that matched or satisfied the path expression. For exampleand in one embodiment, the names of the one or more flagged nodes may beappended (e.g., hierarchically or otherwise) to form an address orindicator of an element of the content 699. Where a path expressionmatches against one or more trace loops in the node stack 677, the Xpathengine 689 may identify one or more elements of the content 699 asmatching the path expression.

Although some of the steps described above may be identified asperformed by the Xpath engine 689 or by some component or module of theXpath engine 689, it should be understood that any other component ormodule of the system may perform the same or substantially the samesteps in various embodiments without departing from the spirit and scopeof the invention. In addition, although generally described with respectto a stack of nodes, it should be recognized that the present systemsand methods may operate on any suitable data structure that representsreceived content 699. Moreover, although generally described above withrespect to an Xpath expression 678 or path expression, it should berecognized that any other suitable types of expression can be used formatching elements in received content 699 in accordance with the systemsand methods disclosed herein.

In some embodiments, the methods described may be modified or combinedwith one or more related methods. The modification or combination may beimplemented in response to the context of the content 699 and/or Xpathexpression 678 received, and/or for performance reasons. One embodimentof a method for Xpath matching uses a finite state automaton (FSA) tomatch possible nodes top to bottom (i.e., from the root node towards theleaf nodes). Events that trigger state transition may be due to the oneor more nodes that are encountered. Events that trigger state transitionmay be due to matching of steps of the Xpath expression 678. Matchingcan be done on either absolute or relative Xpaths (i.e., any portion ofthe Xpath expression 678 including one or more steps). The latter mayhave more state transitions, since the actual match might start atdifferent points in the document and also a partial match might fail butoverlap another possible match (e.g. //a/b/c applied to a document thathas /a/b/a/b/c). The Xpath engine 689 may match multiple Xpathssimultaneously. Multiple simultaneous matching may be modeled asseparate automata or as a union automaton that has multiple recognitionactions.

In this top-to-bottom method, many states may be needed to match therequired Xpath expressions 678. In some embodiments, this may use upsignificant memory that could be used for other purposes to improveperformance. Processor caches could be strained by the extra data. Thismay be especially true in the presence of non-absolute Xpaths and/ormultiple simultaneous Xpaths. In addition, with non-absolute Xpaths many“false starts” (i.e., that does not result in a match) may result in theperformance of multiple unnecessary steps. For example, this may be truewhere the steps near the leaf are more discriminating. In oneembodiment, the top-to-bottom method may be implemented withbacktracking to handle alternative matching portions of the pathexpression. However, in some of these embodiments, streaming may not besupported.

In one embodiment, the top-to-bottom method may result in exponentialstate blowup to handle alternatives in the face of multiple simultaneousXpath expression 678s, or at least a large set of states, which can hogmemory. In some embodiments, this is exacerbated when the Xpaths are notabsolute. In some embodiments, the top-to-bottom method may result inslower performance in cases where the initial part of the pathexpression matches frequently but the end part of the path usually doesnot match. In some embodiments, the most unique part of the path is ator near the leaf.

In another embodiment, a bottom to top matching method may be used. Aselements are encountered during parsing of the document, these elementsmaybe stored on a stack. End element events can “pop” the element“pushed” by the corresponding start element event. In some embodiments,leaf steps of the Xpath expression 678 are put in a hash map (e.g., fornamed nodes). The node type may be used to index into an array of leafsteps (e.g., for unnamed nodes). The entry (e.g., to the hash and/orindex) may be the expression to match against the document. In someembodiments, each of these entries really are a list of expressions tomatch (since we are matching multiple Xpath expressions). Wildcards andnode( ) may be treated specially by putting their expressions inmultiple lists. Each expression may match from the bottom leaf node upthe stack to the first node in the expression, with a non-match for theexpression occurring if any step does not match or we went past the endof the stack. Expression matching may re-occur on a leaf which matcheseach node as they are encountered in the document.

In some embodiments, the bottom to top method may have one or moreissues or limitations. In the bottom-to-top method, the documentinformation used by the non-leaf Xpath expression 678 steps would haveto be recorded on the stack. In one embodiments, the stack may needpotentially a lot of information, e.g., if non-trivial matching isperformed on non-leaf steps. In some embodiments, all or substantialamounts of information from the document is needed to do matching of thestep, e.g., element name and attribute information from elements. Thiscan be a lot of information to copy to the stack, especially when manyattributes and/or long attribute values are involved. Such copying mayreduce performance—directly in doing allocation, memory copies, anddeallocation—and indirectly because the processor cache may be strained.

In some embodiments, looping may be needed for some constructs, forexample descendant axes (including “//”). The matching may be slower incases where the leaf node cannot be finely differentiated (such asunnamed nodes and wildcards) or when a matching leaf node name (which ispart of a path that does not match) occurs many times in the document.This may be attributed to the many “false starts” that can occur.

In some embodiments, we may use embodiments of the method described inconnection with FIG. 6B (sometimes referred to as a “hybrid” method,e.g., in relation to the top to bottom method and the bottom to topmethod) for expressions that have attribute predicates on non-leafsteps. In certain embodiments, this is because there is some cost tomatching steps, e.g., when predicates need to be evaluated. In someembodiments, we may apply the bottom to top method, or the top to bottommethod, to the received content 699. In certain embodiments, based oninformation from document statistics or even well-known documentschemas, the system can determine which method or combination of methodscan perform better in the specific situation. For example and in oneembodiment, in determining how discriminating the first steps or partsof the Xpath expression 678 are when compared to the last parts or stepsof the Xpath expression 678, the system may determine whether to use abottom-to-top or top-to-bottom method. Based on information from theXpath, the system may determine which method or combination of method touse. For example and in one embodiment, absolute paths may work betterin some embodiments using a top-to-bottom method. In some embodiments,bottom-to-top may not perform well for expressions with wildcards onleaf nodes.

It should be understood that the systems described above may providemultiple ones of any or each of those components and these componentsmay be provided on either a standalone machine or, in some embodiments,on multiple machines in a distributed system. In addition, the systemsand methods described above may be provided as one or morecomputer-readable programs or executable instructions embodied on or inone or more articles of manufacture. The article of manufacture may be afloppy disk, a hard disk, a CD-ROM, a flash memory card, a PROM, a RAM,a ROM, or a magnetic tape. In general, the computer-readable programsmay be implemented in any programming language, such as LISP, PERL, C,C++, C#, PROLOG, or in any byte code language such as JAVA. The softwareprograms or executable instructions may be stored on or in one or morearticles of manufacture as object code.

While the invention has been particularly shown and described withreference to specific embodiments, it should be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdefined by the following claims.

What is claimed is:
 1. A method for efficient Xpath matching of anExtensible Markup Language (XML) or JavaScript Object Notation (JSON)document, the method comprising: (a) identifying, by a device, an Xpathexpression for processing values in a document comprising ExtensibleMarkup Language (XML) or JavaScript Object Notation (JSON), the documentrepresented by a stack of nodes; (b) traversing, by the device, thestack of nodes from top to bottom to match each step of a pathexpression of the Xpath expression to a type and name of one or morenodes in the stack of nodes, the stack of nodes comprising the name ofthe node and a flag indicating a matching step; (c) storing, by thedevice, the flag with each node in the stack of nodes that matches astep of the path expression; (d) responsive to encountering a leaf node,tracing, by the device, bottom to top from the leaf node through each ofthe flagged nodes in the stack of nodes, and comparing each of theflagged nodes against a corresponding step of the path expression; and(e) determining, by the device responsive to the tracing through theflagged nodes, whether the path expression is matched based on whetherthere are enough nodes in the stack of nodes to match a minimum numberof steps remaining in the path expression and each step in the pathexpression is matched to a corresponding flagged node.
 2. The method ofclaim 1, wherein step (a) further comprises identifying an Xpathexpression for identifying an element or location in the document. 3.The method of claim 1, wherein step (a) further comprises assigning astep identifier to each step of the path expression.
 4. The method ofclaim 1, wherein step (b) further comprises matching an expression ofeach step, including any predicate, with a type and a name of one ormore nodes in the stack of nodes.
 5. The method of claim 1, wherein step(b) further comprises determining that the path expression is notmatched if any single step of the path expression fails to match anynodes.
 6. The method of claim 1, wherein step (b) further comprisesperforming a loop trace for one or more descendant axes in the pathexpression, wherein the loop trace comprises tracing one or more nodesmatching the descendant axes.
 7. The method of claim 1, wherein step (c)further comprises storing a Boolean flag with each node in the stack ofnodes that matches a step of the path expression.
 8. The method of claim7, further comprising determining that there are enough nodes in thestack to match the minimum number of steps remaining in the pathexpression.
 9. The method of claim 1, wherein step (e) further comprisesdetermining that the path expression is not matched if the stack ofnodes runs out of nodes before reaching the first step of the pathexpression while tracing bottom to top.
 10. The method of claim 1,wherein step (e) further comprises determining that the path expressionis matched if a node of the stack of nodes corresponding to the firststep of the path expression is flagged.
 11. A system for efficient Xpathmatching of an Extensible Markup Language (XML) or JavaScript ObjectNotation (JSON) document, comprising: a device; a parser processing adocument comprising Extensible Markup Language (XML) or JavaScriptObject Notation (JSON) document and representing the document as a stackof nodes; and an Xpath engine executing on the device, comprising: anexpression evaluator identifying an Xpath expression for processingvalues in the document, a node tracer traversing the stack of nodes fromtop to bottom to match each step of a path expression of the Xpathexpression to a type and name of one or more nodes in the stack ofnodes, storing a flag in each node in the stack of nodes that matches astep of the path expression, and responsive to encountering a leaf node,tracing bottom to top from the leaf node through each of the flaggednodes in the stack of nodes, comparing each of the flagged nodes againsta corresponding step of the path expression, wherein the expressionevaluator, responsive to the tracing through the flagged nodes,determines whether the path expression is matched based on whether thereare enough nodes in the stack of nodes to match a minimum number ofsteps remaining in the path expression and each step in the pathexpression is matched to a corresponding flagged node.
 12. The system ofclaim 11, wherein the Xpath expression comprises an expression foridentifying an element or location in the document.
 13. The system ofclaim 11, wherein the expression evaluator matches an expression of eachstep, including any predicate, with a type and a name of one or morenodes in the stack of nodes.
 14. The system of claim 11, wherein theexpression evaluator assigns a step identifier to each step of the pathexpression.
 15. The system of claim 11, wherein the expression evaluatordetermines that the path expression is not matched if any single step ofthe path expression fails to match any nodes.
 16. The system of claim11, wherein the flag stored in each node in the stack of nodes thatmatches a step of the path expression comprises a Boolean flag.
 17. Thesystem of claim 11, wherein the node tracer performs a loop trace forone or more descendant axes in the path expression, the loop tracecomprising tracing one or more nodes matching the descendant axes. 18.The system of claim 17, wherein the node tracer determines that a numberof nodes in the stack match a minimum number of steps remaining in thepath expression.
 19. The system of claim 11, wherein the expressionevaluator determines that the path expression is not matched if thestack of nodes runs out of nodes before reaching the first step of thepath expression while tracing bottom to top.
 20. The system of claim 11,wherein the expression evaluator determines that the path expression ismatched if a node of the stack of nodes corresponding to the first stepof the path expression is flagged.